"I don’t identify as gay, but I do identify as bisexual," Gillum told Tamron Hall in an interview that aired Monday. "That is something I’ve never shared publicly before.”
The admission comes after a difficult year for Gillum, once a rising star in the Democratic Party.
In March, he checked into rehab to seek treatment for alcoholism and depression after he was discovered by police in a Miami hotel room intoxicated and with another man who was said to have overdosed. Police said they found what appeared to be crystal meth in the hotel room, although Gillum has denied taking the drug.
Gillum declined to directly answer a question from Hall about his intention upon entering the hotel room that night, but did say, "I understand very well what people assume about that."
The 41-year-old former mayor of Tallahassee has previously said that losing the race for governor had weighed heavily on him.
He told Hall he had been ashamed after a photo of him passed out naked in the hotel room was published by a British tabloid.
“When that photo came out, I didn’t recognize the person on the floor," he said. "That was not anything more than a person being at their most vulnerable state, unconscious, having given no consent, and someone decided to use a moment where I was literally lying in my own vomit.”
Gillum's wife, R. Jai, told Hall she knew of her husband's sexuality prior to their marriage.
“So many people just don’t understand bisexuality," R. Jai said in the joint interview. "Bisexuality is just something different. I just believe that love and sexuality exist on a spectrum. All I care about is what’s between us and what agreement we make.”
Andrew Gillum also told Hall that it was not appropriate to link bisexuality with infidelity.
"Bisexuality in and of itself doesn't lead to unfaithfulness," he said. "There are men who are in marriages with women who just because they're married to a woman doesn't mean they're not attracted to other women, and at any point can slip up, make a mistake, do something, and that is what it is. The same thing in bisexual relationships.
"You can be attracted to both, you got a bigger terrain out there that you have to contend with, but you can still choose to be physically with one person."