The hosts were struggling to find their rhythm and were indebted to Marshall for keeping them level as he made an excellent save to tip Johnnie Jackson's free kick onto the post before the ball was cleared.
Bellamy was in action again just before the break as he latched onto Craig Noone's ball into the penalty area, following good work down the left by Andrew Taylor, but he could only head wide.
After the break, Charlton were still threatening and Ricardo Fuller forced Marshall into another good save as he turned in the penalty area before firing a low shot which the keeper tipped round the post.
Cardiff thought that they had taken the lead when Noone turned the ball home from close range after Mutch had lifted it into the area only for the goal be ruled out by the linesman for offside.
The hosts tried their utmost to get a winner but they were held back by a stubborn Charlton backline.
However, their failure to find a breakthrough didn't matter as they were promoted to the Premier League by earning a precious point.