Mosaic artist, sculptor, painter, and printmaker Isaiah Zagar was born Irwin Zagar in 1939 in Philadelphia, Pennsylvania, and was raised in Brooklyn, New York. His formal education began at Emerson College, during which time he took a trip to Woodstock to visit Outsider artist Clarence Schmidt's "art environment," called Mirrored Hope, in 1959. Schmidt's seven story labyrinthine structure, consisting of found objects, mirrors, and mosaics artfully pieced together with roofing tar, was built into a mountainside. Zagar was greatly inspired by Schmidt's home and work and, intent on becoming an artist, he enrolled at the Pratt Institute of Art, where he received his B.F.A. in painting and graphics in the early 1960s.

Upon graduation from Pratt, Zagar met and married his wife, Julia, herself an artist who studied at Cooper Union and the University of the Americas in Mexico City, and together they joined the Peace Corps. They were sent to Peru where they remained for three years. Zagar often credits his time there for inspiring his love of folk art. It was also around this time that he took up the name Isaiah.

When the Zagars returned from Peru in 1968 they settled in South Philadelphia and opened the Eyes Gallery which featured folk art from around the world. Zagar created his first mosaic on the walls of the gallery. He soon built a reputation for his large-scale mosaics, assemblages, and murals, and was commissioned to create works for the city of Philadelphia as well as for private clients. In the mid 1990s he began working on his largest project, mosaicking his entire property and two adjacent lots that would eventually become known as Philadelphia's Magic Gardens, which has since become a non profit supporting local artists.

Zagar completed residencies in Tianjin, China and Rajasthan, India, as well as a residency at the Kohler Co. Pottery Foundation in Wisconsin. He was awarded grants by the National Endowment for the Arts and the Pew Charitable Trusts, and his work is held in the collections of the Philadelphia Museum of Art and the Pennsylvania Academy of the Fine Arts. He continues to work and has hosted art shows in the Magic Gardens that feature international folk artists. A documentary about his life titled "In a Dream", filmed by his son Jeremiah Zagar, debuted in 2008.