Charlie Austin scored after 41 seconds to lift Southampton over former manger Ronald Koeman and Everton at St Mary’s.
Austin’s ninth goal of the season gave Southampton the early advantage, which the hosts defended valiantly.
Koeman — making his return to the south coast having left for Everton in the summer — has just one win from eight Premier League matches (1W, 3D, 4L).
But it was Southampton securing all three points for the first time since defeating Burnley on 16 October.
Austin headed in from point-blank giving Saints a 1-0 lead after debutant Josh Sims teed up the striker following a cross into the box.
Looking to add to his early assist, Sims found space in the box, but sent a powerless header into the hands of Maarten Stekelenburg on 17 minutes.
Yannick Bolasie had a chance to put Everton’s first shot on target in the 55th minute, but his vicious effort on the counter attack beat the far upright.
Southampton nearly doubled the lead three minutes later when Austin rose to meet Cedric’s cross only to see Stekelenburg make the save at full stretch.
James Ward-Prowse then went close on 78 minutes, as his right-footed strike from 25 yards forced a save, but Austin couldn’t pounce on the rebound.
The midfielder had another chance to poke the ball past Stekelenburg, who made the initial save before Phil Jagielka cleared the deflection off the line.
Gareth Barry failed to wrap his foot around an effort in added time sent straight at Fraser Forster, who had little to do as Everton only had one shot on target.
Southampton: Forster, Bertrand, van Dijk, Fonte (c), Cedric, Romeu, Hojbjerg, Ward-Prowse, Sims (McQueen 84), Redmond (Clasie 79), Austin (Long 89).
Unused subs: Taylor (GK), Yoshida, Reed, Rodriguez.
Goals: Austin (1).
Everton: Stekelenburg, Baines (Valencia 83), Jagielka (c), Williams, Coleman, Barry, Gueye, Bolasie, Barkley (Mirallas 71), Lennon (Deulofeu 65), Lukaku.
Unused subs: Joel (GK), Cleverley, Funes Mori, Holgate.
Bookings: Lukaku (78).