Sean was born in Detroit, where he grew up. When he was six, his parents divorced, after which his father, an Army sergeant, was mostly absent from his life, sending a Casio watch to him every year on his birthday. Sean's mother, Patricia Sasser, continued to raise Sean and his younger sister. Sean attended a private school, which he said was probably not typical of most African-American young people in urban Detroit.
He later attended Cass Technical High School, a select college-preparatory magnet school. After high school, Sean attended the University of Chicago to study Near Eastern civilizations and become an archeologist. However, he found himself bored and depressed, and barely completed his freshman year. He dropped out of college, intending initially to take a year off.
After he came out as gay to his devoutly religious mother, he attempted to enlist in the United States Navy, explaining in a 1997 interview, "I didn't want to be gay anymore. I thought it would work. You know, the discipline, all that stuff." Before he could leave his home, however, a mandatory blood test revealed that the 19-year-old Sasser was HIV-positive. He decided to enroll in culinary school, as he had always been fond of cooking, and wanted to open his own restaurant.
After finishing school, Sean found jobs cooking in local Chicago restaurants, but was too fixated on the idea of dying from AIDS. Realizing that he "needed to figure out how to keep living", he moved to San Francisco, whose greater HIV awareness and diversity allowed him to find people he more easily related to – specifically, HIV-positive people closer to his own age – which raised his spirits. Sean joined a youth HIV-positive movement that advocated attention for adolescents with the disease, and began speaking to groups about his own experience with HIV.
Sean attended the 1993 Lesbian and Gay March on Washington, where he introduced himself to a fellow AIDS educator named Pedro Zamora. Although Sean did not characterize his meeting Zamora as love at first sight (they were both involved with other people at the time), he was moved by Zamora's presence and conviction, recalling, "I was kind of like, 'Wow.' I had never run across someone who was as good at it as he was."
Sean encouraged Zamora to call him if Zamora ever visited San Francisco. Sean subsequently learned that producers of The Real World were looking for an HIV-positive person to cast in the 1994 season in San Francisco season, where Sean had been living for a couple of years, and eventually learned that the person cast was Zamora, whom Sean felt was ideal for the role.
Sean had been living in San Francisco for a couple of years in the 1990s. When Zamora moved into The Real World San Francisco loft, he and Sean began dating. Zamora asked the show's producers for permission to go out on the second date without cameras, so that he and Sasser could get to know one another in a more natural setting.
After the producers allowed this, Sasser and Zamora fell in love, and their relationship became a focal point of the season. After production on The Real World ceased in June 1994, Zamora visited his family in Miami before returning to San Francisco to live with Sean. In August 1994, Zamora was diagnosed in New York City with progressive multifocal leukoencephalopathy (PML), and was given three to four months to live.
On September 3, Zamora was flown to Mercy Hospital in Miami, where his family could be close to him. His family was not accepting of Sean Sasser, however, and because the PML gradually took away Zamora's ability to speak, Zamora was unable to explicitly communicate to them the importance of Sean in his life. This led to confrontations between Sean and the Zamoras, who told him that "Pedro did not need to have a lover anymore", and mostly excluded Sean from Zamora during his final days.
Zamora died on November 11, 1994. Sean Sasser returned to San Francisco two days later. Six months after Zamora's death, he resumed his speaking engagements for LGBT and HIV issues. In 1995, he spoke at the inaugural White House AIDS conference, and was appointed by President Bill Clinton to the Presidential Advisory Council on HIV/AIDS. He moved to Atlanta in late 1995, in order to be with his boyfriend, and hoped to open a café.
Sasser was a pastry chef at Ritz-Carlton hotel properties and head pastry chef at The Nines, a luxury hotel in Portland, Oregon. He moved to Washington, D.C. in 2012, where, as a pastry chef at a restaurant called RIS, he was praised by the Washington Blade for his homemade ice cream and sorbets.
In June 2013, Sean Sasser married Michael Kaplan, whom he had dated off and on since the 1990s, and with whom he had moved in six years prior. While living in the District, Sean served as a board member of the AIDS Alliance for Children, Youth and Families. He was active in youth and mentoring organizations, and he and Kaplan served as foster parents to a 4-year-old girl.
In July 2013, Sean, who had been HIV-positive for 25 years, was also diagnosed with mesothelioma, a rare cancer of the lungs. Sean had no known occupational exposure to asbestos, the primary cause of mesothelioma, though studies suggest that "chronic immunosuppression enhances susceptibility to mesothelioma."
He died at his home, at the age of 44. In accordance with his wishes, his body was cremated, and his ashes spread upon places he had been or wished to visit. He is survived by his husband, Michael.