The agency, which was hired following a pitch, will create a campaign urging viewers to act on their impulse to change their job.
The work will star actor Max Beesley, who plays deputy manager Charlie Edwards in BBC1's luxury hotel drama Hotel Babylon.
The first raft of activity is due to launch next month. It will include TV, print, digital and radio work. Two further bursts are scheduled for later in the year. The TV campaign will run in prime-time slots on ITV, Channel 4, Five and Sky.
For the online element of the campaign, the brand will increase its digital spend by 50%. Online activity will include paid search, e-mail marketing and display advertising.
Earlier this year, Jobsite partnered RecruitLondon for a joint recruitment advertising package with the Evening Standard, London Lite and Metro, to broaden its reach both online and offline. Recruitment ads from each of the titles' advertisers appeared on Jobsite, while the website's branding ran across each of the papers' print issues.
Jobsite, which launched in 1995, has more than 4.1m registered users and features a range of blogs from high-profile businesspeople, including Birmingham City Football Club managing director Karren Brady.