Maher was born in New York City, the son of Julie (née Berman), a nurse, and William Maher, Sr., a network news editor and radio announcer. Maher was raised in his Irish American father's Catholic religion, and did not find out that his mother was Jewish until his teenage years. He grew up in River Vale, New Jersey and graduated from Pascack Hills High School in Montvale, New Jersey. He received his Bachelor of Arts in English and History from Cornell University in 1978.

Maher began his career as a stand-up comedian and actor, and he continues to act and tour occasionally. He was host of the New York City comedy club Catch a Rising Star in 1979. Thanks to Steve Allen, he began appearing on Johnny Carson's and David Letterman's shows in 1982. He made limited television appearances, including two separate appearances on Murder She Wrote -- notably, as Maher likes to point out, as two different characters. He has also appeared in several films, usually in a comic role. His feat