After graduating from New York University in 1987 with a degree in communications, Attell worked menial jobs during the day and put in his time at comedy clubs at night. He worked his first gig at Governor's in Levittown and, according to Attell, "totally bombed".
Attell's first appearance on television was in 1988 on VH1's Stand-Up Spotlight, which also featured early appearances by Lewis Black, Margaret Cho, Jeff Garlin, Jay Mohr and Wanda Sykes. The show was hosted by Rosie O'Donnell.
Perhaps his biggest break was achieved on November 23, 1993, when he made his first appearance on The Late Show with David Letterman. The appearance was seen by Saturday Night Live creator Lorne Michaels, who then recruited Attell to be a Writer, and occasional performer, on SNL. Attell can be seen behind Chris Farley during the famous "Rudy Giuliani Inauguration" Sketch. Attell worked on the show for the 1993–94 season.
In 1995, Attell appeared as Squiggly Dave on Dr. Katz, Professional Therapist. In 1999, the network issued Attell an installment in their Comedy Central Presents series.
The same year the network signed him on as a regular commentator on their satirical news show The Daily Show. When he arrived in 1999, the show was just finding its audience after the departure of host Craig Kilborn and the arrival of Jon Stewart, an old friend of Attell's from the New York comedy circuit. The three-year stint gave Attell access to a mass audience on a regular basis (The Daily Show has done much the same for comedians Stephen Colbert, Steve Carell, Lewis Black and others). Attell's series of commentary on the show was called "The Ugly American". He appeared in the finale for The Daily Show with Jon Stewart. In 2003, Attell began appearing semi-regularly on Tough Crowd with Colin Quinn. The show featured many of the performers he works with every day at the underground comedy club the Comedy Cellar and is based on the conversations they would have off-stage at the Olive Tree Cafe, the restaurant above the club. The unscripted show was canceled in November 2004.
Attell provided humorous in-game commentary for the 2005 PlayStation 2 and Xbox game Outlaw Golf 2.
In 2007, Attell appeared in the Michael Addis film, Heckler. Attell also appeared on Comedy Central's Last Laugh in 2007.
He plays the character Barker in the 2008 comedy film Harold.
He voiced the GPS on the Mystery Machine in the 2010 film Scooby-Doo! Abracadabra-Doo.
Attell returned to television on Showtime beginning October 20, 2011 in Dave's Old Porn, a TV series in which Attell views and jokes about retro 1970s and 1980s pornographic movies with different guest comedians. Typically, during a given show, Attell and his guest view clips that give an overview of a particular retro porn star's career. Near the end of that show, that particular porn actor appears and also comments on clips from some of his or her movies.
In April 2014, Comedy Central premiered Comedy Underground with Dave Attell, a late night, (mostly) uncensored stand-up comedy show taped live in New York.
