The couple has been going on "a couple of dates," with a source claiming "it's on" between both stars, reported Ace Showbiz.
Last week, the rumoured new lovers were spotted having a great time together at the Cinema Against AIDS gala for amfAR at the Hotel du Cap-Eden-Roc.
The 20-year-old model, who recently split from singer boyfriend Cody Simpson, looked gorgeous wearing an almost-there white dress by Tom Ford that exposed her cleavage and slim legs.
Hamilton, meanwhile, looked dapper in black suit and bow tie.
The twosome sat next to each other during the event and managed to take photos together. Hamilton has been single following his separation from on-and-off-girlfriend Nicole Scherzinger earlier this year.