The 23-year-old singer performed 'I Knew You Were Trouble' at the ceremony - held at London's The O2 venue on Wednesday night - and security were on high alert to ensure the blonde beauty didn't bump into or even look at her ex-boyfriend, whose band One Direction performed their new charity single 'One Way Or Another (Teenage Kicks)'.
A source told the Daily Mirror newspaper: "Taylor and her people passed Harry backstage and a security guard barked, 'Look left!' so there was no eye contact."
Harry - who split from Taylor after two months of dating over New Year - was the butt of BRITs host James Corden's jokes throughout the evening, with him making references to the 19-year-old lothario's interest in older women.
James quipped: "Sharon Osbourne's here, Annie Lennox is here. So tell me [Harry], who've you got your eye on, then?"
Sharon, 60, also joined in when she presented an award, joking: "Where is that little Harry Potter boy? Has he got his little magic stick with him tonight? That's his willy."
Later in the evening at the Sony Music after party - held in association with Belvedere vodka - Harry said he had enjoyed his ex-girlfriend's performance, telling website MailOnline: "I thought her performance was really good, she looked great."
One Direction - also including Niall Horan, Liam Payne, Louis Tomlinson and Zayn Malik - took home the BRITs Global Success Award at the event.