The Greek striker had a mostly dreadful game but his goal made the difference at Parkhead as both teams served up a poor match.
Regardless of the spectacle, the win allowed Celtic to move two points clear at the summit, however Rangers – in Scottish Cup semi-final action on Sunday – now have three games in hand.
Scott Severin almost provided a dream start when he tried his luck from 25 yards with a shot which struck the inside of Artur Boruc’s right-hand post and trickled along the goal-line before hitting the other upright.
Bobo Balde scooped over the bar from close range, but Celtic took the lead on 56.
Samaras threw himself in front of Barry Robson’s free-kick and nodded home from eight yards.