diff --git a/src/lib/components/collection/AddToCollectionModal.svelte b/src/lib/components/collection/AddToCollectionModal.svelte
new file mode 100644
index 00000000..3132f07a
--- /dev/null
+++ b/src/lib/components/collection/AddToCollectionModal.svelte
@@ -0,0 +1,447 @@
+<script lang="ts">
+	import { createQuery, createInfiniteQuery } from '@tanstack/svelte-query'
+	import { searchAdapter, type SearchResult } from '$lib/api/adapters/search.adapter'
+	import { collectionQueries } from '$lib/api/queries/collection.queries'
+	import { useAddCharactersToCollection } from '$lib/api/mutations/collection.mutations'
+	import Dialog from '$lib/components/ui/Dialog.svelte'
+	import Button from '$lib/components/ui/Button.svelte'
+	import Icon from '$lib/components/Icon.svelte'
+	import CollectionFilters, {
+		type CollectionFilterState
+	} from './CollectionFilters.svelte'
+	import SelectableCharacterCard from './SelectableCharacterCard.svelte'
+	import { IsInViewport } from 'runed'
+
+	interface Props {
+		open?: boolean
+		onOpenChange?: (open: boolean) => void
+	}
+
+	let { open = $bindable(false), onOpenChange }: Props = $props()
+
+	// Search state
+	let searchQuery = $state('')
+	let debouncedQuery = $state('')
+	let debounceTimer: ReturnType<typeof setTimeout>
+
+	// Filter state
+	let elementFilters = $state<number[]>([])
+	let rarityFilters = $state<number[]>([])
+	let seasonFilters = $state<number[]>([])
+	let seriesFilters = $state<number[]>([])
+	let raceFilters = $state<number[]>([])
+	let proficiencyFilters = $state<number[]>([])
+	let genderFilters = $state<number[]>([])
+
+	// Selection state
+	let selectedIds = $state<Set<string>>(new Set())
+	let showOnlySelected = $state(false)
+
+	// Refs
+	let sentinelEl = $state<HTMLElement>()
+
+	// Get IDs of characters already in collection
+	const collectedIdsQuery = createQuery(() => collectionQueries.collectedCharacterIds())
+
+	// Build filters for search
+	const searchFilters = $derived({
+		element: elementFilters.length > 0 ? elementFilters : undefined,
+		rarity: rarityFilters.length > 0 ? rarityFilters : undefined,
+		season: seasonFilters.length > 0 ? seasonFilters : undefined,
+		characterSeries: seriesFilters.length > 0 ? seriesFilters : undefined,
+		// Note: Race, proficiency, and gender filters would need API support
+		// For now we filter client-side or skip if API doesn't support
+		proficiency1: proficiencyFilters.length > 0 ? proficiencyFilters : undefined
+	})
+
+	// Search query with infinite scroll
+	const searchResults = createInfiniteQuery(() => ({
+		queryKey: ['search', 'characters', 'collection', debouncedQuery, searchFilters] as const,
+		queryFn: async ({ pageParam }) => {
+			const response = await searchAdapter.searchCharacters({
+				query: debouncedQuery || undefined,
+				page: pageParam,
+				per: 60,
+				filters: searchFilters,
+				exclude: collectedIdsQuery.data ?? []
+			})
+			return {
+				results: response.results ?? [],
+				page: response.meta?.page ?? pageParam,
+				totalPages: response.meta?.totalPages ?? 1,
+				total: response.meta?.count ?? 0
+			}
+		},
+		initialPageParam: 1,
+		getNextPageParam: (lastPage) => {
+			if (lastPage.page < lastPage.totalPages) {
+				return lastPage.page + 1
+			}
+			return undefined
+		},
+		enabled: open && !collectedIdsQuery.isLoading
+	}))
+
+	// Flatten results
+	const allResults = $derived(
+		searchResults.data?.pages.flatMap((page) => page.results) ?? []
+	)
+
+	// Filter to show only selected if enabled
+	const displayedResults = $derived(
+		showOnlySelected
+			? allResults.filter((r) => selectedIds.has(r.id))
+			: allResults
+	)
+
+	// Add mutation
+	const addMutation = useAddCharactersToCollection()
+
+	// Debounce search input
+	$effect(() => {
+		clearTimeout(debounceTimer)
+		debounceTimer = setTimeout(() => {
+			debouncedQuery = searchQuery
+		}, 300)
+
+		return () => clearTimeout(debounceTimer)
+	})
+
+	// Infinite scroll
+	const inViewport = new IsInViewport(() => sentinelEl, {
+		rootMargin: '200px'
+	})
+
+	$effect(() => {
+		if (
+			inViewport.current &&
+			searchResults.hasNextPage &&
+			!searchResults.isFetchingNextPage &&
+			!searchResults.isLoading &&
+			!showOnlySelected
+		) {
+			searchResults.fetchNextPage()
+		}
+	})
+
+	// Reset state when modal closes
+	$effect(() => {
+		if (!open) {
+			selectedIds = new Set()
+			showOnlySelected = false
+			searchQuery = ''
+			debouncedQuery = ''
+			elementFilters = []
+			rarityFilters = []
+			seasonFilters = []
+			seriesFilters = []
+			raceFilters = []
+			proficiencyFilters = []
+			genderFilters = []
+		}
+	})
+
+	function toggleSelection(character: SearchResult) {
+		const newSet = new Set(selectedIds)
+		if (newSet.has(character.id)) {
+			newSet.delete(character.id)
+		} else {
+			newSet.add(character.id)
+		}
+		selectedIds = newSet
+	}
+
+	function handleFiltersChange(filters: CollectionFilterState) {
+		elementFilters = filters.element
+		rarityFilters = filters.rarity
+		seasonFilters = filters.season
+		seriesFilters = filters.series
+		raceFilters = filters.race
+		proficiencyFilters = filters.proficiency
+		genderFilters = filters.gender
+	}
+
+	function toggleShowSelected() {
+		showOnlySelected = !showOnlySelected
+	}
+
+	async function handleAdd() {
+		if (selectedIds.size === 0) return
+
+		const inputs = Array.from(selectedIds).map((characterId) => ({
+			characterId,
+			uncapLevel: 0,
+			transcendenceStep: 0
+		}))
+
+		try {
+			await addMutation.mutateAsync(inputs)
+			open = false
+			onOpenChange?.(false)
+		} catch (error) {
+			console.error('Failed to add characters:', error)
+		}
+	}
+
+	const selectedCount = $derived(selectedIds.size)
+	const isLoading = $derived(searchResults.isLoading || collectedIdsQuery.isLoading)
+</script>
+
+<Dialog bind:open {onOpenChange} title="Add Characters to Collection" size="large">
+	{#snippet children()}
+		<div class="modal-content">
+			<!-- Search input -->
+			<div class="search-bar">
+				<Icon name="search" size={18} />
+				<input
+					type="text"
+					bind:value={searchQuery}
+					placeholder="Search characters by name..."
+					class="search-input"
+				/>
+			</div>
+
+			<!-- Filters -->
+			<div class="filters-bar">
+				<CollectionFilters
+					bind:elementFilters
+					bind:rarityFilters
+					bind:seasonFilters
+					bind:seriesFilters
+					bind:raceFilters
+					bind:proficiencyFilters
+					bind:genderFilters
+					onFiltersChange={handleFiltersChange}
+					layout="horizontal"
+				/>
+			</div>
+
+			<!-- Results grid -->
+			<div class="results-area">
+				{#if isLoading}
+					<div class="loading-state">
+						<Icon name="loader-2" size={32} />
+						<p>Loading characters...</p>
+					</div>
+				{:else if displayedResults.length === 0}
+					<div class="empty-state">
+						{#if showOnlySelected}
+							<p>No characters selected</p>
+							<Button variant="ghost" size="small" onclick={toggleShowSelected}>
+								Show all characters
+							</Button>
+						{:else if searchQuery || Object.values(searchFilters).some((v) => v)}
+							<p>No characters match your search</p>
+						{:else}
+							<p>Start searching to find characters</p>
+						{/if}
+					</div>
+				{:else}
+					<div class="results-grid">
+						{#each displayedResults as character (character.id)}
+							<SelectableCharacterCard
+								{character}
+								selected={selectedIds.has(character.id)}
+								onToggle={toggleSelection}
+							/>
+						{/each}
+					</div>
+
+					{#if !showOnlySelected && searchResults.hasNextPage}
+						<div class="load-more-sentinel" bind:this={sentinelEl}></div>
+					{/if}
+
+					{#if searchResults.isFetchingNextPage}
+						<div class="loading-more">
+							<Icon name="loader-2" size={20} />
+							<span>Loading more...</span>
+						</div>
+					{/if}
+				{/if}
+			</div>
+		</div>
+	{/snippet}
+
+	{#snippet footer()}
+		<div class="modal-footer">
+			<div class="footer-left">
+				{#if selectedCount > 0}
+					<button
+						type="button"
+						class="selected-link"
+						class:active={showOnlySelected}
+						onclick={toggleShowSelected}
+					>
+						{selectedCount} character{selectedCount === 1 ? '' : 's'} selected
+					</button>
+				{/if}
+			</div>
+			<div class="footer-right">
+				<Button variant="ghost" onclick={() => (open = false)}>
+					Cancel
+				</Button>
+				<Button
+					variant="primary"
+					disabled={selectedCount === 0 || addMutation.isPending}
+					onclick={handleAdd}
+				>
+					{#if addMutation.isPending}
+						<Icon name="loader-2" size={16} />
+						Adding...
+					{:else}
+						Add to Collection
+					{/if}
+				</Button>
+			</div>
+		</div>
+	{/snippet}
+</Dialog>
+
+<style lang="scss">
+	@use '$src/themes/spacing' as *;
+
+	.modal-content {
+		display: flex;
+		flex-direction: column;
+		height: 100%;
+		gap: $unit-2x;
+	}
+
+	.search-bar {
+		display: flex;
+		align-items: center;
+		gap: $unit;
+		padding: $unit-half $unit;
+		background: var(--input-bg, #f5f5f5);
+		border-radius: 8px;
+		border: 1px solid var(--border-color, #ddd);
+
+		:global(svg) {
+			color: var(--text-secondary, #666);
+			flex-shrink: 0;
+		}
+	}
+
+	.search-input {
+		flex: 1;
+		border: none;
+		background: transparent;
+		font-size: 14px;
+		padding: $unit-half 0;
+		color: var(--text-primary, #333);
+
+		&::placeholder {
+			color: var(--text-tertiary, #999);
+		}
+
+		&:focus {
+			outline: none;
+		}
+	}
+
+	.filters-bar {
+		padding-bottom: $unit;
+		border-bottom: 1px solid var(--border-color, #eee);
+		overflow-x: auto;
+	}
+
+	.results-area {
+		flex: 1;
+		overflow-y: auto;
+		min-height: 0;
+	}
+
+	.results-grid {
+		display: grid;
+		grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
+		gap: $unit;
+		padding: $unit 0;
+	}
+
+	.loading-state,
+	.empty-state {
+		display: flex;
+		flex-direction: column;
+		align-items: center;
+		justify-content: center;
+		height: 200px;
+		color: var(--text-secondary, #666);
+		gap: $unit;
+
+		:global(svg) {
+			animation: spin 1s linear infinite;
+		}
+
+		p {
+			margin: 0;
+		}
+	}
+
+	.load-more-sentinel {
+		height: 1px;
+		margin-top: $unit;
+	}
+
+	.loading-more {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		gap: $unit;
+		padding: $unit-2x;
+		color: var(--text-secondary, #666);
+
+		:global(svg) {
+			animation: spin 1s linear infinite;
+		}
+	}
+
+	.modal-footer {
+		display: flex;
+		align-items: center;
+		justify-content: space-between;
+		width: 100%;
+	}
+
+	.footer-left {
+		flex: 1;
+	}
+
+	.footer-right {
+		display: flex;
+		gap: $unit;
+	}
+
+	.selected-link {
+		background: none;
+		border: none;
+		color: var(--accent-color, #3366ff);
+		font-size: 14px;
+		cursor: pointer;
+		padding: $unit-half $unit;
+		border-radius: 4px;
+
+		&:hover {
+			background: var(--button-bg-hover, #f0f0f0);
+			text-decoration: underline;
+		}
+
+		&.active {
+			background: var(--accent-color, #3366ff);
+			color: white;
+
+			&:hover {
+				background: var(--accent-color-hover, #2255ee);
+				text-decoration: none;
+			}
+		}
+	}
+
+	@keyframes spin {
+		from {
+			transform: rotate(0deg);
+		}
+		to {
+			transform: rotate(360deg);
+		}
+	}
+</style>
diff --git a/src/lib/components/collection/SelectableCharacterCard.svelte b/src/lib/components/collection/SelectableCharacterCard.svelte
new file mode 100644
index 00000000..140fe06e
--- /dev/null
+++ b/src/lib/components/collection/SelectableCharacterCard.svelte
@@ -0,0 +1,100 @@
+<script lang="ts">
+	import { getCharacterImage } from '$lib/utils/images'
+	import Icon from '$lib/components/Icon.svelte'
+	import type { SearchResult } from '$lib/api/adapters/search.adapter'
+
+	interface Props {
+		character: SearchResult
+		selected?: boolean
+		onToggle?: (character: SearchResult) => void
+	}
+
+	let { character, selected = false, onToggle }: Props = $props()
+
+	const imageUrl = $derived(
+		getCharacterImage(character.granblueId, 'grid', '01')
+	)
+
+	const name = $derived(
+		typeof character.name === 'string'
+			? character.name
+			: character.name?.en || character.name?.ja || 'Unknown'
+	)
+
+	function handleClick() {
+		onToggle?.(character)
+	}
+
+	function handleKeyDown(e: KeyboardEvent) {
+		if (e.key === 'Enter' || e.key === ' ') {
+			e.preventDefault()
+			handleClick()
+		}
+	}
+</script>
+
+<button
+	type="button"
+	class="card"
+	class:selected
+	onclick={handleClick}
+	onkeydown={handleKeyDown}
+	aria-pressed={selected}
+	aria-label="{selected ? 'Deselect' : 'Select'} {name}"
+>
+	<img src={imageUrl} alt={name} class="image" loading="lazy" />
+	{#if selected}
+		<div class="check-overlay">
+			<Icon name="check" size={24} />
+		</div>
+	{/if}
+</button>
+
+<style lang="scss">
+	@use '$src/themes/spacing' as *;
+	@use '$src/themes/effects' as *;
+
+	.card {
+		position: relative;
+		width: 80px;
+		height: 80px;
+		padding: 0;
+		border: 2px solid transparent;
+		border-radius: 8px;
+		background: var(--card-bg, #f5f5f5);
+		cursor: pointer;
+		overflow: hidden;
+		@include smooth-transition(0.15s, all);
+
+		&:hover {
+			border-color: var(--accent-color, #3366ff);
+			transform: scale(1.02);
+		}
+
+		&:focus-visible {
+			outline: 2px solid var(--focus-ring, #3366ff);
+			outline-offset: 2px;
+		}
+
+		&.selected {
+			border-color: var(--accent-color, #3366ff);
+			box-shadow: 0 0 0 2px var(--accent-color, #3366ff);
+		}
+	}
+
+	.image {
+		width: 100%;
+		height: 100%;
+		object-fit: cover;
+	}
+
+	.check-overlay {
+		position: absolute;
+		inset: 0;
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		background: rgba(51, 102, 255, 0.6);
+		color: white;
+	}
+</style>