Balk lives in Venice, California, and has an apartment in New York City. Outside her career, her interests include writing poetry and fiction, playing guitar, singing, and dancing. Over the years she has been romantically involved with a number of well known men including British actor David Thewlis who appeared with her in The Island of Dr. Moreau (1996) and in American Perfekt (1997), and C. M. Talkington too, director and writer of the cult classic, Love and a .45.[citation needed]

She was a well known neopagan even before shooting 1996's The Craft. She provided some witchcraft information on set and helped design many of the sets to match real pagan rituals. From 1995 to 2001, she owned Panpipes Magickal Marketplace, billed as the nation's largest occult store, in Hollywood, California.