Burnley had been desperately clinging on for a draw with the match approaching the final 12 minutes, but Mark McGregor was adjudged to have fouled former Boro man Campbell in the box and Richard Langley broke the visitors' spirits from the spot.
Campbell then added a second when John Robinson played in the young forward to smash home only his second goal of the season.
The game before the goals had been a nervous gritty affair.
McGregor had headed an early corner over the bar for Burnley and top scorer Robbie Blake was denied by a save by Martyn Margetson.
Langley had fired two shots wide for the hosts, but it took the introduction of Campbell by manager Lennie Lawrence (Pictured) to finally turn the match in Cardiff's favour.
Burnley are now only outside the relegation places by dint of a superior goal difference to Gillingham - but Stan Ternent will be well aware that his side must start to take points if they are to stay up.
