The 44-year old actor - who split from Amy Poheler in September 2012 after nine years of marriage - has "quietly" ended his brief romance with producer Erin David and has now struck up a relationship with the 28-year-old actress.
A source told Us Weekly magazine: "Will and Erin were on and off for a while."
The 'Teenage Mutant Ninja Turtles' star was seen with Arielle at the 25th annual KROQ Acoustic Christmas in Los Angeles last month and insiders say the pair share a similar sense of humour.
Another source said: "She loves to laugh. The past few girls haven't been fun enough for him, he's a child at heart."
Since splitting from Amy - with who he has sons Archie, six, and Abel, four - over two years ago, Will has also been romantically linked with celebrity chef Katie Lee.
The 'Parks and Recreation' actress - who is now dating comedian Nick Kroll - recently insisted she is "proud" of how she and Will handled their separation and doesn't view their divorce as a failure.
She wrote in her autobiography 'Yes Please': "I am proud of how my ex-husband, Will, and I have been taking care of our children. I am beyond grateful he is their father; and I don't think a 10-year marriage constitutes failure."
tagged in Amy Poehler