After graduating from law school, Bloom began her career in New York and by 1991 worked at her mother’s law firm, Allred, Maroko & Goldberg, assisting in unsuccessfully suing the Boy Scouts of America for sex discrimination on behalf of Katrina Yeaw, a girl who wanted to join the organization. While at her mother’s firm, Bloom also filed a child sexual abuse suit against the Roman Catholic Church and sued the LAPD.

In 2001 Bloom left her mother’s firm, having parlayed her legal and familial notoriety into a lucrative career in cable news punditry, eventually serving as a legal analyst on CBS News, CNN, HLN, and MSNBC, and appearing on The Early Show, The Insider, Dr. Phil, Dr. Drew, The Situation Room, Reliable Sources, The Joy Behar Show, Issues with Jane Velez-Mitchell, and The Stephanie Miller Show. Bloom returned to practicing law in 2010 when she founded the Bloom Firm, a small, general-practice law firm that handles family, civil and Criminal matters. She is licensed to practice law in both New York and California.

Bloom founded and owns a twelve-attorney civil rights law firm, the Bloom Firm, and has represented clients including Kathy Griffin and Mischa Barton. Bloom was also the anchor of Lisa Bloom: Open Court (formerly Bloom and Politan: Open Court), a two-hour live legal news program on truTV's In Session, from 2006 to 2009.

Bloom has written three books, including Think: Straight Talk for Women to Stay Smart in a Dumbed-Down World, from 2011, and Swagger: 10 Urgent Rules for Raising Boys in an Era of Failing Schools, Mass Joblessness, and Thug Culture, from 2012. In early 2017, The Weinstein Company and Jay-Z announced plans to adapt Bloom's 2014 book, Suspicion Nation: The Inside Story of the Trayvon Martin Injustice and Why We Continue to Repeat It, into a six-part documentary series. The status of the project is unknown following turmoil at the Weinstein Company.

Bloom married her current husband, Braden Pollock, on December 5, 2014. Pollock is the founder of Legal Brand Marketing and now works as the Bloom Firm's firm manager. Bloom has two adult children, Sarah and Sam, and lives with her husband and a foster son in Los Angeles. A vegetarian since 16, Bloom has been vegan since 2009. She identifies as Jewish.

On November 2, 2016, Bloom canceled a press conference with "Jane Doe" saying her client was scared because of death threats. According to Bloom, after this press conference, "Multiple donors then contacted me out of the blue with offers to ensure the safety of women who might still come forward. As an attorney I was obligated to relay those offers of funds for relocation to a safer community and round the clock security, and I was happy to do it." The Virginian woman said that Bloom had offered her as much as $750,000, but that she ultimately declined the offer and did not come forward. One of the donors reportedly helped Harth pay off her mortgage. The New York Times identified these donors as David Brock's American Bridge 21st Century, which offered $200,000, and Susie Tompkins Buell, who offered $500,000.

Bloom and her firm are representing male model Jason Boyce in his lawsuit against fashion Photographer Bruce Weber among other people in New York State Supreme Court in December 2017.

At the Bloom Firm, Bloom has represented several notable clients, including model and Actress Janice Dickinson in her defamation case against Comedian Bill Cosby, as well as model and Actress Mischa Barton in her revenge porn case. Model Blac Chyna later hired Bloom to obtain a temporary restraining order against socialite Rob Kardashian, with whom Chyna shares a daughter, Dream. Amid a series of sexual abuse allegations against powerful men in entertainment and media, and following a BuzzFeed report detailing a sexual harassment settlement paid out of Representative John Conyers’ office budget, Bloom represented Marion Brown, who spoke to BuzzFeed off the record and later came forward publicly to allege harassment by Conyers.