The England full-back’s clinical finishing laid the platform for an impressive opening 40 minutes from Steve McNamara’s men, who led 22-12 at the break.
Centre Brayden Wiliame also touched down for the Dragons while Innes Senior and Jake Wardle were Huddersfield’s first-half scorers.
Catalans underlined their superiority with a second-half brace from winger Jodie Broughton but further home tries by Darnell McIntosh, Lee Gaskell, and Senior in the final quarter ensured a tense finale.
For Huddersfield, despite their spirited late rally, this was a major setback after they had won at Salford last week to halt a run of four successive defeats. The result leaves the Giants just two points above bottom-placed London and in the thick of the scrap to avoid the drop.
Tomkins opened the scoring in the eighth minute when he collected Samisoni Langi’s pass, added the simple conversion and claimed his second try seven minutes later.
Langi found Tony Gigot and the stand-off’s teasing grubber kick bounced invitingly for Tomkins to ground the ball for a try he converted to make it 12-0.
Huddersfield had some respite in the 22nd minute when the ball was worked out to homegrown winger Senior, who touched down in the left corner.
Wigan scored further tries from Wiliame and Tomkins before a teasing kick from scrum-half Tom Holmes was seized upon by Wardle, who added his second conversion to make it 22-12 at the break.
Broughton finished clinically in the left corner and then did likewise from a similar position.
McIntosh went over from close range in the 63rd minute for a try which Wardle converted before Gaskell scythed through the visiting defence for a fine individual score while Catalans lost Kenny Edwards to the sin-bin late on.
Huddersfield made their numerical advantage pay when Senior crossed in the left corner for his second try and Wardle’s fourth goal cut the gap to four points - but Catalans held on.
Huddersfield: McIntosh, McGillvary, Gaskell, Clough, Leeming, Murphy, Mellor, Ta’ai, J. Wardle, Holmes, Ikahihifo, L. Senior, I. Senior. Substitutes: Frawley, Matagi, Lawrence, Wilson.
Catalans Dragons: Tomkins, Broughton, Mead, Wiliame, Romano, Langi, Gigot, Bousquet, McIlorum, Simon, Whitley, Garcia, Casty. Substitutes: Edwards, Albert, Maria, Kasiano.
Referee: Greg Dolan (RFL).