The win in Naples sees Walter Mazzarri's side take their tally to 49 points from 23 matches.
© AP Photos
The Neapolitan outfit were always in control of the match at Stadio San Paolo despite some early pressure from Catania and took the lead on the half-hour mark.
Cavani himself almost made it 2-0 to Napoli in the 38th minute when his free kick was pushed on to the Catania crossbar.
It did eventually become 2-0 to the home side four minutes later as Hamsik set up Paolo Cannavaro to slot home from just six yards.
Gonzalo Bergessio thought that he had pulled one back for the visitors in the 47th minute when he headed home a corner, but it was ruled out for shirt-pulling.
Napoli soon created their own chance, as Cavani fired over the bar after the hour mark.
The former Italian champions, though, failed to add to their tally in the second period and settled for a 2-0 win.