Outdoor clothing brand Regatta has signed the pair up, along with Michaela Strachan and Peter Duncan.
They will appear in print ads this month, running in titles such as the Daily Mail, Country Living and The Observer Magazine. The campaign was photographed by John Rankin.
Oddie has been chosen as he is a famous twitcher, and presents BBC television programmes 'Springwatch' and 'Autumnwatch'.
Janet Street-Porter is vice-president of the Ramblers and famous for her love of walking.
The campaign strapline may raise some eyebrows, with one ad proclaiming: "Bill Oddie wears it out… birdwatching on a London heath."
Graham Rickard, marketing director at Regatta, said: "Each portrait incorporates our strap line 'Wear it out' alongside a description of where and what activity the celebrities were captured doing."