Thinkbox has appointed Mother as its creative agency and is working on a TV campaign planned for later this year.
The agency won the business in a pitch handled by AAR and competed against Bartle Bogle Hegarty London, Leo Burnett and Wonderhood Studios.
Thinkbox marketing director Andrew MacGillivray commended the runners-up for some "cracking scripts".
"We were privileged to see such high quality across the board," he said. "The whole pitch process has confirmed that the UK’s creative agencies are bursting with wonderful TV ideas."
But ultimately the TV marketing body opted for Mother on the basis of its "spot-on strategy, a brilliant creative platform and some truly sparkling creativity".
Thinkbox called the review in May, marking a split with Red Brick Road, which had handled the account for 12 years.
Red Brick Road had produced an array of work for Thinkbox, including 2012's "Harvey and Rabbit" and "The broadcast" in 2016 that saw aliens using TV to announce their plan to take over Earth.
Chris Gallery, strategy partner at Mother, said: "It’s no surprise that we love TV ads at Mother and now we get to make a TV ad for TV ads. We can’t wait to get started working with the Thinkbox team."
While Thinkbox would not divulge details, messaging will promote TV's efficacy as an ad medium, backed by stats such as that commercial TV reaches 89% of the UK every week, according to 2018 Barb figures, while an average broadcast TV campaign in the UK accrues 240 million views.
Thinkbox's media planning and buying business is unaffected and continues to be led by MediaCom.