diff --git a/cmd/msgvault/cmd/remove_account.go b/cmd/msgvault/cmd/remove_account.go
index 12f14503..95677854 100644
--- a/cmd/msgvault/cmd/remove_account.go
+++ b/cmd/msgvault/cmd/remove_account.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/spf13/cobra"
@@ -26,8 +27,8 @@ and mbox), use --type to specify which one to remove.
 The Parquet analytics cache is deleted because it is shared across accounts
 and must be rebuilt. Run 'msgvault build-cache' afterward to rebuild it.
 
-Orphaned participants and attachment files on disk are not cleaned up;
-use 'msgvault gc' (when available) to reclaim that space.
+Attachment files on disk that are not shared with another account are deleted.
+Shared attachments (same content hash across multiple accounts) are kept.
 
 Examples:
   msgvault remove-account you@gmail.com
@@ -114,10 +115,113 @@ func runRemoveAccount(cmd *cobra.Command, args []string) error {
 		}
 	}
 
+	// Collect attachment paths unique to this source before the cascade deletes them.
+	attachmentPaths, err := s.AttachmentPathsUniqueToSource(source.ID)
+	if err != nil {
+		return fmt.Errorf("collect attachment paths: %w", err)
+	}
+
+	// Check for any running syncs BEFORE RemoveSource. sync_runs rows for this
+	// source are cascade-deleted along with the source, so checking afterward
+	// would miss a running sync on the account being removed.
+	//
+	// Attachment ingestion writes the file first (StoreAttachmentFile) and
+	// inserts the DB row second (UpsertAttachment). Deleting files while any
+	// sync is in that window can remove a blob that a concurrent writer has
+	// already placed on disk but not yet recorded. We skip file deletion
+	// entirely in that case; the DB removal still proceeds.
+	skipFileDeletion := false
+	skipReason := ""
+	if len(attachmentPaths) > 0 {
+		anySyncRunning, err := s.HasAnyActiveSync()
+		if err != nil {
+			skipFileDeletion = true
+			skipReason = fmt.Sprintf("could not check for active syncs: %v", err)
+		} else if anySyncRunning {
+			skipFileDeletion = true
+			skipReason = "a sync is in progress"
+		}
+	}
+
 	if err := s.RemoveSource(source.ID); err != nil {
 		return fmt.Errorf("remove account: %w", err)
 	}
 
+	// Delete attachment files that are no longer referenced by any source.
+	attachmentsDir := cfg.AttachmentsDir()
+	var deletedFiles int
+	if len(attachmentPaths) > 0 {
+		if skipFileDeletion {
+			// The account DB rows are gone but files remain. Since the account
+			// no longer exists, the user cannot re-run remove-account; direct
+			// them to the attachments directory instead.
+			fmt.Fprintf(os.Stderr,
+				"Warning: %s; attachment files were not deleted.\n"+
+					"Orphaned files may remain in %s\n",
+				skipReason, attachmentsDir,
+			)
+		} else {
+			// No syncs were running when we checked. Re-check each path
+			// immediately before deletion as a last-ditch guard: after
+			// RemoveSource the cascade has cleared this source's attachment
+			// rows, so IsAttachmentPathReferenced will catch any new reference
+			// a concurrent sync for a different source may have inserted.
+
+			// Resolve attachmentsDir to an absolute path once so the
+			// containment check below works correctly regardless of the
+			// process working directory.
+			cleanDir, err := filepath.Abs(attachmentsDir)
+			if err != nil {
+				fmt.Fprintf(os.Stderr,
+					"Warning: could not resolve attachments dir; skipping file deletion: %v\n", err,
+				)
+				cleanDir = ""
+			}
+
+			var failedFiles int
+			for _, relPath := range attachmentPaths {
+				absPath := filepath.Join(cleanDir, relPath)
+
+				// Guard against a corrupt or tampered DB entry that could
+				// otherwise cause os.Remove to target a file outside the
+				// attachments directory via path components such as "..".
+				if cleanDir != "" {
+					rel, err := filepath.Rel(cleanDir, absPath)
+					if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
+						fmt.Fprintf(os.Stderr,
+							"Warning: attachment path %q escapes attachments directory, skipping\n",
+							relPath,
+						)
+						failedFiles++
+						continue
+					}
+				}
+
+				if referenced, err := s.IsAttachmentPathReferenced(relPath); err != nil {
+					fmt.Fprintf(os.Stderr,
+						"Warning: could not verify attachment %s is unreferenced: %v\n",
+						relPath, err,
+					)
+					failedFiles++
+					continue
+				} else if referenced {
+					continue
+				}
+				if err := os.Remove(absPath); err != nil && !os.IsNotExist(err) {
+					failedFiles++
+				} else {
+					deletedFiles++
+				}
+			}
+			if failedFiles > 0 {
+				fmt.Fprintf(os.Stderr,
+					"Warning: could not remove %d attachment file(s) from disk.\n",
+					failedFiles,
+				)
+			}
+		}
+	}
+
 	// Remove credentials for the source type.
 	switch source.SourceType {
 	case "gmail":
@@ -183,13 +287,12 @@ func runRemoveAccount(cmd *cobra.Command, args []string) error {
 	}
 
 	fmt.Printf("\nAccount %s removed.\n", email)
+	if deletedFiles > 0 {
+		fmt.Printf("Deleted %d attachment file(s) from disk.\n", deletedFiles)
+	}
 	fmt.Println(
 		"Run 'msgvault build-cache' to rebuild the analytics cache.",
 	)
-	fmt.Println(
-		"Note: attachment files on disk were not removed." +
-			" Use 'msgvault gc' (when available) to reclaim space.",
-	)
 
 	return nil
 }
diff --git a/internal/store/messages.go b/internal/store/messages.go
index f3384c5c..c2beaad0 100644
--- a/internal/store/messages.go
+++ b/internal/store/messages.go
@@ -1220,6 +1220,62 @@ func (s *Store) UpsertMessageRawWithFormat(messageID int64, rawData []byte, form
 	return err
 }
 
+// AttachmentPathsUniqueToSource returns storage_path values for attachments
+// belonging to sourceID whose content_hash is not shared with any other source.
+// Call this before RemoveSource so the cascade hasn't run yet.
+//
+// Note: thumbnail_path values are not included. No sync/import code currently
+// writes thumbnail files to disk, so there are no thumbnail files to clean up.
+// If thumbnail storage is added in the future, this function and the delete
+// loop in remove_account.go must be extended to cover thumbnail_path as well.
+func (s *Store) AttachmentPathsUniqueToSource(sourceID int64) ([]string, error) {
+	rows, err := s.db.Query(`
+		SELECT DISTINCT a.storage_path
+		FROM attachments a
+		JOIN messages m ON m.id = a.message_id
+		WHERE m.source_id = ?
+		  AND a.content_hash IS NOT NULL
+		  AND a.storage_path IS NOT NULL
+		  AND a.storage_path != ''
+		  AND NOT EXISTS (
+		      SELECT 1 FROM attachments a2
+		      JOIN messages m2 ON m2.id = a2.message_id
+		      WHERE a2.content_hash = a.content_hash
+		        AND m2.source_id != ?
+		  )
+	`, sourceID, sourceID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var paths []string
+	for rows.Next() {
+		var p string
+		if err := rows.Scan(&p); err != nil {
+			return nil, err
+		}
+		paths = append(paths, p)
+	}
+	return paths, rows.Err()
+}
+
+// IsAttachmentPathReferenced returns true if any attachment record still
+// points to the given storage_path. Use this immediately before deleting a
+// file to guard against a concurrent sync that added a new reference after
+// the candidate list was collected.
+func (s *Store) IsAttachmentPathReferenced(storagePath string) (bool, error) {
+	var count int
+	err := s.db.QueryRow(
+		`SELECT COUNT(*) FROM attachments WHERE storage_path = ?`,
+		storagePath,
+	).Scan(&count)
+	if err != nil {
+		return true, err // fail safe: treat error as referenced
+	}
+	return count > 0, nil
+}
+
 // UpsertAttachment stores an attachment record.
 func (s *Store) UpsertAttachment(messageID int64, filename, mimeType, storagePath, contentHash string, size int) error {
 	// Check if attachment already exists (by message_id and content_hash)
diff --git a/internal/store/schema.sql b/internal/store/schema.sql
index 1a584330..e84a13a4 100644
--- a/internal/store/schema.sql
+++ b/internal/store/schema.sql
@@ -357,6 +357,7 @@ CREATE INDEX IF NOT EXISTS idx_reactions_message ON reactions(message_id);
 -- Attachments
 CREATE INDEX IF NOT EXISTS idx_attachments_message ON attachments(message_id);
 CREATE INDEX IF NOT EXISTS idx_attachments_hash ON attachments(content_hash);
+CREATE INDEX IF NOT EXISTS idx_attachments_storage_path ON attachments(storage_path);
 
 -- Labels
 CREATE INDEX IF NOT EXISTS idx_labels_source ON labels(source_id);
diff --git a/internal/store/sync.go b/internal/store/sync.go
index b4a0ddf2..713b0edf 100644
--- a/internal/store/sync.go
+++ b/internal/store/sync.go
@@ -234,6 +234,20 @@ func (s *Store) GetActiveSync(sourceID int64) (*SyncRun, error) {
 	return run, err
 }
 
+// HasAnyActiveSync returns true if any source currently has a running sync.
+// Use this as a safety gate before performing destructive file operations that
+// could race with concurrent attachment ingestion.
+func (s *Store) HasAnyActiveSync() (bool, error) {
+	var count int
+	err := s.db.QueryRow(
+		`SELECT COUNT(*) FROM sync_runs WHERE status = 'running'`,
+	).Scan(&count)
+	if err != nil {
+		return true, err // fail safe
+	}
+	return count > 0, nil
+}
+
 // GetLastSuccessfulSync returns the most recent successful sync for a source.
 func (s *Store) GetLastSuccessfulSync(sourceID int64) (*SyncRun, error) {
 	row := s.db.QueryRow(`