The museum was created by Marion Koogler McNay's original bequest of most of her fortune, her important art collection and her 24-room Spanish Colonial Revival-style mansion that sits on 23 acres (9.3 ha) that are landscaped with fountains, broad lawns and a Japanese-inspired garden and fishpond.

McNay was an American painter and art teacher who inherited a substantial oil fortune upon the death of her father.

The museum was named after her, and has been expanded to include galleries of medieval and Renaissance artwork and a larger collection of 20th-century European and American modernist work.

The McNay Art Museum added the Jane and Arthur Stieren Center for Exhibitions in 2008, built by architect Jean-Paul Viguier, to display their Modern collection.

The center's design, materials, and architectural details both contrast with and complement the original Spanish Colonial Revival-style residence, which it adjoins.