Neither side had won in their previous five games, but Whittingham's fine finish from a Craig Noone cross in the 65th minute gave the hosts a merited three points and opened up a little breathing space to the bottom three for Malky Mackay's side.
It was Albion's fourth straight defeat and manager Steve Clarke will be as concerned as fellow Scot Mackay was relieved by this result.
The best early chance fell to Steven Caulker, Turner flicked on Whittingham's corner but the England centre-half put his shot wide with Myhill stranded out of position.
Cardiff pressed again at the start of the second half, but it was West Brom who carved out the clearest chance yet when Morgan Amalfitano pulled back to Claudio Yacob.
The Argentinian scuffed his shot to McAuley who made a better fist of hitting the target, only for Gary Medel to block on the line, with Marshall also in attendance.
Cardiff hit back and took the lead. The excellent Noone delivered a pinpoint cross which Whittingham headed wide of Myhill's despairing dive into the bottom corner.
The game had suddenly sprung to life and West Brom had a decent penalty shout turned down by referee Howard Webb.
Long appeared to be bundled over by Turner as he turned in the box, but the Republic of Ireland striker was waved to his feet.
But their final chance came and went when a Long header was brilliantly saved by a full-stretch Marshall.
- Sports & Recreation
- Malky Mackay
- Gareth McAuley