His producer, Fraser Lawson, will join him.
Arnell moved from Pagan Films to Blink a year ago, claiming that he wanted to move away from directing music videos and rekindle his commercials career.
In the 11 months he spent at Blink, Arnell directed a handful of ads, including an O2 spot for VCCP and a forthcoming Carlsberg commercial for Saatchi & Saatchi.
Arnell was formerly a director at the now-defunct production outfit Godman, where he directed the award-winning Levi's "creek" spot for Bartle Bogle Hegarty, and Stella Artois' "red shoes" and "the good Samaritan" for Lowe. He began his career as a runner at the Gordon Lewis Organisation, before joining Chase Films.
After moving to Pagan Films, Arnell focused on music videos, directing a string of promos for the pop star Robbie Williams.
He said: "I'm really excited to be joining Sonny. It feels like a fresh beginning - it's one of the most exciting production companies in London, and everyone there has loads of great ideas."
Bond quit MJZ London to launch Sonny in February.