Susan Keane (Brooke Shields) has always been taken care of by someone else. She worked as a copy editor at The Gate, a fictional San Francisco magazine. On her wedding day, she realizes that she and her wealthy, vain fiancé, Kip, are not meant for each other and that there is more to life than just being known as the "s" in "The Kip Richmonds." She abruptly leaves him at the altar. Now, she's suddenly just Susan. Susan's parents (guest stars Swoosie Kurtz and Ray Baker) were less than ecstatic about their daughter deciding to end her engagement to Kip, though her grandmother and confidant, Nana (Barbara Barrie), stands as a pillar of support for Susan.

The day after the wedding, Susan goes to her boss, Jack Richmond (Judd Nelson), the rebellious brother of Susan's former fiancé, Kip, begging for her job back. Instead, Jack assigns Susan to write a regular column about being suddenly single. Susan's coworkers include photographer Luis Rivera (Néstor Carbonell), boyish rock music reporter Todd Stites (David Strickland), restaurant critic Vicki Groener (Kathy Griffin), and, in later episodes, investigative reporter and Susan's old enemy Maddy Piper (Andréa Bendewald).

In the show's final season, The Gate is taken over by Ian Maxtone-Graham (Eric Idle) and overhauled into a men's magazine that is run out of an old warehouse in Chinatown. Along with this, Ian brings his own team of workers, including executive assistant and U.S. Navy veteran Miranda Charles (Sherri Shepherd), sportswriter Nate Knaborski (Currie Graham), and freelancer photographer Oliver Browne (Rob Estes). Susan is faced with a new set of problems and has to prove herself all over again.

Besides the task of putting together a magazine and focusing on the lead character's life, Suddenly Susan also focuses on the private lives of many employees in the show.

• Brooke Shields as Susan Keane
• Néstor Carbonell as Luis Rivera, Susan's co-worker and Gate photographer
• Kathy Griffin as Vicki Groener, Susan's co-worker and Gate food/nightlife writer
• Judd Nelson as Jack Richmond, Susan's boss and original love interest (Seasons 1–3)
• David Strickland as Todd Stites, Susan's co-worker and Gate music critic (Seasons 1–3)^{[note 1]}
• Barbara Barrie as Helen 'Nana' Keane, Susan's grandmother
• Andréa Bendewald as Maddy Piper, Susan's co-worker and former high school rival, and Gate journalist (Seasons 2–3; guest star, Season 4)^{[note 2]}
• Currie Graham as Nate Knaborski, Susan's co-worker and Gate sportswriter (Season 4)
• Eric Idle as Ian Maxtone-Graham, Susan's boss (Season 4)^{[note 3]}
• Sherri Shepherd as Miranda Charles, Ian's executive assistant (Season 4)^{[note 4]}
• Rob Estes as Oliver Browne, Susan's love interest and Gate freelance photographer (Season 4)^{[note 5]}

In the show's original pilot, written by Billy Van Zandt and Jane Milmore and based on a dramatic script by Clyde Phillips, Susan worked at a publishing house editing children's books. After breaking up with her live-in boyfriend Ted (Brian McNamara), Susan finds herself "single" for the first time in years. Concurrently, Susan faces even greater challenges at work when her boss, Eric (Philip Casnoff), assigns her the task of working as an editor with Charlotte (Elizabeth Ashley), a hugely successful and highly opinionated romance novelist. Always on hand to provide support is Susan's grandmother, Nana (Nancy Marchand), her co-workers, acerbic best friend Marcy (Maggie Wheeler) and Neil (David Krumholtz), who has a crush on Susan.

When the series was picked up, former Murphy Brown writers/producers Gary Dontzig and Steven Peterman were brought in to redevelop the concept, being appointed as the show's co-showrunners. Other changes between the pilot and the series included Barbara Barrie replacing Nancy Marchand in the role of Nana, and Swoosie Kurtz and Ray Baker replacing Kurt Fuller and Caroline McWilliams as Susan's parents, Bill and Liz; the characters of Eric and Ted were reworked into the roles of Jack Richmond (played by Nelson) and his brother, Kip (Anthony Starke), whom Susan jilts during their wedding. (McNamara would later play Cooper Elliot, a friend of Jack's who briefly replaces him as publisher of The Gate through a poker game bet and takes Susan to Italy at the end of Season 1.) In the series, though the setting switches from a publishing house to a magazine, the main office set retained most of its features from the pilot; the most noticeable difference was that the elevator was at stage right. While the pilot's storyline featuring Elizabeth Ashley as one of the publishing house's clients was not used in the series, a cardboard cut out of Ashley that was featured in the pilot appears throughout the first three seasons of the show – it can be seen briefly behind Susan's desk, near the filing cabinets along the back wall.

The actual location for the exterior shots of the office was the Newhall Building at 260 California Street in San Francisco.

David Strickland died by suicide in a Las Vegas motel room on March 22, 1999. Strickland's death was later incorporated into the show's third season finale, "A Day in the Life", which killed off his character, Todd Stites. The episode's plot finds Susan desperately trying to find Todd when she suspects he has gone missing after he fails to show up to work one morning. As the episode progresses, Susan learns about a number of good deeds that Todd had done around his neighborhood that she never knew about. In-character interviews with the supporting cast also appear throughout the episode, with each actor sharing their personal experiences they had with Strickland before his death, framed as each character's own memories of Todd. As the episode comes to an end, Todd's favorite song, "Praise You" by Fatboy Slim, plays outside of Luis' apartment as Susan and her co-workers sit in a circle praying for Todd's well-being. At last, the phone in the middle of the room rings, but the camera cuts away before the news of Todd's fate can be revealed. The episode ends with memorable clips of Strickland from the show and the memorial subtitle: "The Gods of comedy looked down upon you and smiled".

Before production began on the fourth and final season, Judd Nelson and Andrea Bendewald left the show; Peterman and Dontzig also stepped down as showrunners, and the series replaced almost its entire writing staff (with the exception of executive producer Maria Semple, who joined the show at the start of Season 3 and took over showrunning duties alongside Mark Driscoll, one of the new writers hired for the fourth season). The departures of Nelson and Bendewald, along with the death of Strickland, prompted Driscoll and Semple to retool the series: The Gate was transformed into a men's magazine by its new owner, Ian Maxtone-Graham (Eric Idle), and relocated from its trendy uptown offices overlooking the bay to a dingy former warehouse in Chinatown. In tow, Ian brought his own team of workers, including executive assistant and U.S. Navy veteran Miranda Charles (Sherri Shepherd), sports writer Nate Knaborski (Currie Graham), and freelance photographer Oliver Browne (Rob Estes). Faced with new challenges, Susan suddenly had to prove herself all over again.

Airing between Seinfeld and ER during its first season, Suddenly Susan was initially a ratings success, attracting almost 25 million viewers per episode,^[82] despite mostly unfavorable critical reviews. When the show was moved to Monday nights at 8:00 p.m. (against the Top 30 hit Cosby) for the second season, the show experienced a large decline in viewership, sliding from #3 to #71 in one year, bringing in less than 11 million viewers. The ratings failed to bounce back, and in its final season, the show barely ranked in the top 100, prompting NBC to pull it from the schedule in January. It returned briefly in June, but at the end of the month was pulled from the network's prime-time schedule with five episodes left unaired. One episode, "The Gay Parade", remained unaired by NBC (but was eventually shown on Lifetime a few years later^[when?]); the final four episodes (including the two-part series finale) were burned off from 2:00 to 4:00 a.m. EST on December 26, 2000, airing as part of the NBC All Night overnight block.

On Rotten Tomatoes, season 1 has an approval rating of 55% based on reviews from 11 critics. The website's critical consensus was: "Comedic inspiration doesn't spark Suddenly for this Susan, hampered by derivative gags that undermine Brooke Shields' energetic performance."^[83]

Caryn James of the New York Times wrote: "Like its lead character, Suddenly Susan has no identity of its own. The beauty of the magic time slot is that it gives Suddenly Susan, with its engaging star and flexible format, a well-deserved chance to grow."^[84][85][86]

Ken Tucker of Entertainment Weekly gave it a grade C and called it: "A wearyingly self-conscious updating of The Mary Tyler Moore Show: nice girl trying to make it in the competitive workplace of a big town."^[87]

^{^[a]} Twenty-three episodes were produced for season four, but episode 18, "The Gay Parade" was never broadcast.^{[92]
^[b]} End of the series' original broadcast run. Last four episodes were aired six months later.^[93]