Livi secured their biggest home league win since 2007 as they demolished Dumbarton 5-0.
The Lions flew at the visitors in the early stages and took the lead on nine minutes.
Iain Russell twisted and turned free down the left before driving the ball across goal, where McNulty was lurking to finish.
It was two nil three minutes later when a Tony Andreu cross was turned home by a bullet Craig Barr header.
The Sons were given a great chance to get back into the game when Bryan Prunty was fouled in the box, but Chris Turner dragged his penalty a yard wide.
And that allowed Livi to further tighten their grip on the three points.
The Lions made them pay on 36 minutes as Russell’s cut back spun into the air, and McNulty finished low into the bottom corner.
Into the second half, McNulty slipped in Russell on 64 minutes, and when Stephan Grindlay parried the former’s low shot, sub Callum Booth was on hand to score with his first touch.
An on fire McNulty then smacked the post from 20 yards and Craig Barr saw an effort ruled out for offside.
But Livi did round off a fine showing on 78 minutes as Keaghan Jacobs’ free kick sailing over the wall and dropped into the net.
In the late stages Andy McNeil topped off an already superb performance with two great saves – the first from a low header from Chris Turner, and then a brilliant block from Sons winger Scott Agnew.
The win was Livi’s first of the season at home, and moved the side up two places in the league standings.
McNeil, Docherty, Garcia Tena, Watson, C.Barr, Kn.Jacobs, Andreu, I.Russell (R.Gray 79), McNulty, Scougall (Booth 64), Morton (Easton 73)
Subs not used: Fordyce, Jamieson
Grindlay, Devlin, McNiff (Creaney 46), Lithgow, Forsyth, Agnew, Fleming, Turner, Lister, Prunty (Johnston 46), Lamont (McDougall 85)
Subs not used: Lyden, Ewings
Referee: George Salmond
Official Attendance: 1, 021
Match report: Calum Leslie
Pictures: Steven Carrie