"My mother had two friends and they were my guncles [gay uncles], and I would put on plays for my guncles.
"I think it was a thing that helped me in my life, being around all different people."
By performing on Saturday night, Carey fulfilled a promise made to fans and Pride's organisers in 2020.
She had been booked to headline that year, but the Covid-19 pandemic meant the annual event was cancelled.
During the performance at Brighton Pride, Carey sang Hero and Fantasy, along with Sugar Sweet from her upcoming 16th studio album, Here For It All.
Since her career began in the late 1980s, Carey has had three UK number one singles and two UK number one albums.
One of her best known songs is All I Want For Christmas Is You.