The Channel 4 drama — starring Years & Years frontman Olly Alexander — which told the story of the HIV epidemic among London's gay community in the 1980s, was in the running for seven gongs.
Alexander, 31, starred as aspiring actor Ritchie Tozer in the drama created by Doctor Who and Queer As Folk writer Russell T Davies, and was up for best leading actor, which went to Sean Bean for his role in prison drama Time.
The Years & Years singer wrote on social media after the ceremony: "BAFTAS !!! So so so happy to be back with my It’s A Sin family..
"We had 11 nominations at this years BAFTAS !!! that’s really amazing!! thank you so much for all the love for the show and congratulations to all the winners tonight. I LOVE BEING GAY."
Davies shared a picture of the cast at the TV Baftas ceremony on Instagram and said: "Look at these winners. We had a very happy night. Great shows won and great shows didn’t, and UK TV is wonderful. Long live #ItsASin."
But some fans of the show were disappointed and felt It's A Sin had been unfairly overlooked by Bafta.
Professional swimmer and reality TV star Michael Gunning tweeted: "We don’t always get recognition for our achievements, but the true winners leave a lasting legacy behind & change our mindsets forever! Thank you #ItsASin… you are a true #BAFTA Winner in our eyes."
Doctor Who star and Dalek operator Barnaby Edwards commented: "No awards? Either BAFTA can’t recognise ground breaking television drama when they see it or they simply don’t like the gays. I’m hoping it’s the former. #ItsASin."
Novelist Melanie Blake said: "#ItsASin was THE drama of that year. Absolutely dreadful snub."
Lydia West, 28, who played Ritchie's best friend and gay rights campaigner lost out on the best leading actress gong to Jodie Comer for Channel 4's Help, which tackled the care crisis during the coronavirus pandemic.
The show was also up for best mini-series, which went to BBC drama Time and the Must-See Moment Award, which was voted for by the public. Viewers voted Strictly Come Dancing winner Rose Ayling-Ellis' silent Couple's Choice dance the winner of that award.
It's A Sin had received 11 TV Bafta nominations in total, including recognition for Davies' writing.
Director Peter Hoar did take home Best Director at the 2022 Bafta TV Craft Awards in April, where Sarah Brewerton was also awarded the Best Editing for Fiction gong for the show.
Watch: Richard Ayoade hosted the TV Baftas