The 17-year-old had prompted fans to speculate earlier in the week when she shared another social media post with her 31 million followers on TikTok in which she mimed the words to Lady Gaga's song 'Born This Way'.
That video included her miming the lyrics: ""No matter gay, straight or bi, lesbian transgender life, I'm on the right track baby I was born to survive."
She was also wearing one of her signature hair bows covered in rainbows, causing yet more speculation from her fans.
Although, as many rightly pointed out, you shouldn't assume people's sexuality because of a song they mime or a hair accessory that they wear.
Wait for them to tell you, if they want to, and feel comfortable doing so.
Well, it would seem as if she's decided that now is the time.
She captioned the post of her wearing the t-shirt: "My cousin got me a new t-shirt."
Since she shared that picture, it has been liked more than 820,000 times and retweeted nearly 125,000 times.
Fans have been queuing up to praise her for her decision to come out. It is tough, after all.
One person wrote: "YES JOJO I LOVE YOU!!! i'm so proud of you, all the love for you."
Another simply said: "We will always support you".
A third wrote: "If God hates gays, how come we keep on winning?"
Rapper Lil Nas X, who came out himself in 2019, turned out to support her. He wrote: "If u spell 'swag' backwards, it's 'gay.' coincidence??"
JoJo started her career as a young child on the show Dance Moms before branching out into a careers as a YouTuber, musician, and children's entertainer.
She's got a number of music videos with more than 100 million views, and also had a smash hit with 'BOOMERANG' - when she was just 13 - that has nearly one billion streams.
JoJo has even been listed on TIME magazine's annual list of the 100 most influential people in the world.
Her trademark hairbows have also helped her to launch a worldwide fashion and accessories brand, and she's starred in TV movies, as well as a number of Nickelodeon shows and Fox's The Masked Singer.
Not bad, given that she's still only 17 years old.
Featured Image Credit: PA