The search engine selected Grand Union from a shortlist of six agencies pitching for a place on its £2m roster alongside lead strategic agency Fallon. The shortlist is believed to have also included Agency.com, Agency Republic, Hyper Happen and Glue.
Ask.com has briefed Grand Union on several initiatives due to roll out over the coming year, intended to increase the firm's share of the £1.2bn UK search sector.
The review has been overseen by Ask.com's head of UK marketing Sarah Bartlett, who joined the company from BT last year. It follows Ask.com's controversial 'Information revolution' campaign, which launched earlier this year to tempt internet users away from Google.
Ask.com has previously worked with Profero on digital projects, but the pair parted company earlier this year following strategic differences.