At the time, the rumoured couple were seen attending a scaled down wedding for Styles' manager at the San Ysidro Ranch in Montecito, California.
"They were affectionate around their friends, held hands and looked very happy. They have dated for a few weeks," a source told People.
Watch: Behind the scenes of Harry Styles' Vogue photoshoot. Post continues below.
Wilde and Styles met after the singer was cast alongside Chris Pine and Florence Pugh in Wilde's upcoming movie, Don't Worry, Darling.
"Olivia and Harry are together for long days on set and have gotten to know each other really well, so it's all very organic," a source told Entertainment Tonight.
"[Olivia] wouldn't let a romantic relationship get in the way of a professional one, so anything they're doing is being done thoughtfully."
The rumours surrounding Wilde and Styles surfaced just months after news broke about Wilde's split from actor Jason Sudeikis.
The couple, who share two children together — son Otis Alexander, six, and daughter Daisy Josephine, four — were engaged for seven years.
Although news of their separation broke in November, sources claimed that their relationship had ended much earlier.
"The split happened at the beginning of the year. It's been amicable and they’ve transitioned into a great co-parenting routine," a source close to the couple told People.
"The children are the priority and the heart of the family’s relationship."