Wasps began their season slowly, with successive defeats to Saracens and Sale, and it took the home side an hour to hit first gear on Sunday afternoon, but once they did Irish had little chance of hauling them back.
The visitors held a 13-12 lead at the interval after Scott Staniforth's early try and extended that just after the interval with two further penalties from fly-half Barry Everitt, who finished with 14 points.
But Jonny O'Connor's try brought Wasps to within touching distance and once King's drop goal took them ahead after 57 minutes, Wasps tightened their grip on the match.
Tom Voyce sliced through the Irish defence for the second try and Ayoola Erinle span clear for the third as Wasps opened a 35-19 lead, rendering Staniforth's solo effort in the closing minutes little more than an impressive consolation.
But it was the Exiles who made the start to the game, and camped themselves in the Wasps 22 directly from the kick-off.
It was Staniforth who eventually found the chink, bursting onto Everitt's pass and under the posts untouched.
Everitt converted and then landed a penalty to open a 10-0 lead after 16 minutes as Wasps struggled to work their way into the Irish 22.
They eventually got on the scoreboard through a 20th minute King penalty as Joe Worsley, vying for the England No.8, began to stamp his authority on the game.
Captaining the side and playing his favoured No.8 role with Lawrence Dallaglio amongst the replacements as he recovers from a rib injury, Worsley launched a break from the base of a Wasps scrum 10 metres inside his own half.
The ball was spun wide to the jinking, elusive Voyce down the left before Worsley took hold of possession again through the middle and when Dawson thought he had spotted a gap, referee Dave Pearson pulled up the Irish defence for offside.
It was an attack that turned the tide of the first half and while Irish preserved their line until the interval, the pressure cost them lock Bob Casey who was sin-binned for use of a forearm after 32 minutes.
By the time Casey returned to the fray in first half injury time, King had landed a fourth penalty but Wasps still trailed 13-12 having failed to make the most of the 10 minutes with an extra man.
Everitt then landed two more penalties in the opening minutes of the second half, the second of which came after Wasps lock John Hart had been sin-binned, as Irish worked themselves clear.
But they could not make use of the man advantage either as O'Connor, the increasingly impressive Wasps openside, charged down Everitt's attempted clearance, collected the loose ball and dropped to the deck.
King missed the conversion but landed a drop goal that carried Wasps into the lead for the first time before Voyce scored the kind of try that earned him a place in the England side on the summer tour of New Zealand and Australia.
He carved his way through the Irish defence and had enough pace, power and momentum to reach the line despite Paul Sackey hanging onto his shorts.
King missed the conversion as the ball rolled off the kicking tee but soon after Warren Gatland had made a raft of changes, including the introduction of Dallaglio, he extended Wasps' lead to 25-19 with a fifth penalty.
And the hosts wrapped up victory with six minutes remaining when Erinle, a constant danger to the Irish defence, took the pass from Dawson, spun out of the tackle and crossed under the posts.
For London Wasps:Tries: Voyce, O'Connor, ErinleCon: KingPen: King 5DG: King
For London Irish:Tries: Staniforth 2Cons: Mapletoft, EverittPens: Everitt 4