The two agencies pitched together, and have been appointed with immediate effect to the accounts.
Wren Living previously worked with media agencies including 20:20, according to Nielsen, and produced its creative advertising in-house.
Wren Living spent £8.2 million on media in the 12 months to 31 March 2014, according to Nielsen, and plans to "significantly increase" its spend in the coming year.
Its previous advertising has been focused on national press activity, but future work will aim to raise awareness of the retailer, which has more than 40 shops around the UK.
Goodstuff and Big Al's have begun work on press executions, but will also consider other platforms for campaigns.
Richard Walker, the head of marketing for Wren Living, said: "I can confirm that with immediate effect, Goodstuff have been appointed as the exclusive UK media planners and buyers for Wren Living (along with Big Al's as our creative partners).
"Our intention is to increase our spend significantly over the next 12 months."
Wren Living has shops in cities including London, Glasgow, Bristol, Cardiff and Manchester. It sells fitted kitchens and bathrooms, as well as furniture for homes.