The show became an instant hit upon premiering in 1997, averaging around 11 million viewers per episode, and grew to around 13 million viewers in its second season.

Robert Downey Jr. joined the cast in the fourth season as Ally's boyfriend Larry Paul, coinciding with a ratings stabilization and a fresher visual style from new art director Matthew DeCoste. However, his character was written out after the season due to Downey's struggles with drug addiction.

The fifth and final season had the lowest ratings of the series and was the only season that failed to win any Emmy or Golden Globe awards, leading Fox to cancel the show.

The show sparked feminist controversy, most notably when a June 29, 1998 Time magazine cover juxtaposed Ally McBeal with real-life feminists Susan B. Anthony, Betty Friedan, and Gloria Steinem under the headline 'Is Feminism Dead?' The show later referenced this directly in a 1999 episode where Ally dreams of being called 'the face of feminism' on Time's cover.

Vonda Shepard, a relatively unknown musician before the show, performed regularly as a character in a piano bar frequented by the cast, and her song 'Searchin' My Soul' became the show's theme, though it was never played in full during the opening credits.

Several characters had their own musical leitmotifs: John Cage's was 'You're the First, the Last, My Everything,' Ling Woo's was the Wicked Witch of the West theme from The Wizard of Oz, and Ally herself chose 'Tell Him' after a psychiatrist told her she needed a theme song.

Singer Josh Groban played the role of Malcolm Wyatt in the May 2001 season finale, performing 'You're Still You.' Creator David E. Kelley was so impressed by Groban's performance at a charity event that he wrote a character specifically for him based on the audience's reaction.

Due to music licensing issues, none of the seasons were available on DVD in the United States until 2009, even though the show had already been released with all its original music intact in countries like Italy, Japan, and the UK since 2005.

In 1999, at the height of the show's popularity, a half-hour sitcom-format spinoff called Ally aired in parallel, using re-edited scenes and new footage focused only on Ally's personal life while cutting courtroom plots; only 10 of the 13 produced episodes actually aired before cancellation.

In 2024, cast members Calista Flockhart, Greg Germann, Peter MacNicol, and Gil Bellows reunited at the 75th Primetime Emmy Awards for a choreographed dance to Barry White's 'You're the First, the Last, My Everything,' recreating the show's iconic unisex bathroom.