After their midweek European disappointment Celtic looked weary but still did just enough to record their 12th successive league victory.
The only goal of the match arrived on the half-hour mark when Shaun Maloney slid the ball home from ten yards after beating the visitors' offside trap.
Thistle started the game brightly and some crisp passing led to Ian Black playing Garry Wood through, but the striker delayed too long and the chance was lost.
Andreas Hinkel's pass to Georgios Samaras was just cut out by Grant Munro before Paul Hartley fired in the 30-yard shot which went narrowly over.
Hinkel was next to threaten with a dangerous run into the area, but Scott McDonald's shot from his cross was blocked.
Celtic made the breakthrough when Shunsuke Nakamura's superb pass found Maloney running through the defence and his first-time shot beat Ryan Esson in the Thistle goal.
Maloney then tested the keeper again with a crisp 25-yard shot which Esson did well to push away.
Thistle wasted a good chance just before the interval when Russell Duncan advanced into the box, but rather than shooting he passed to Doug Imrie who skied his effort over.
At the start of the second half Maloney cut in from the left but a dangerous cross along the six-yard line was just too strong for Scott Brown.
Duncan's superb pass found Black in space but the midfielder's shot was too direct and Artur Boruc gathered easily.
Celtic were finding it hard to finish off Thistle and some wayward shooting by Hartley and McDonald did not help their cause.
Thistle were unable to exert any sustained pressure on the home defence and Celtic achieved their target of extending their lead at the top.