DO-HEON Kim further pushed his Barclays Premier League claims as his superb 36th-minute winner capped a fine central midfield display.
The Korea Republic star bagged his second goal in three games by curling home a 20-yard free-kick to earn Tony Mowbray's men their first pre-season win at the sixth attempt.
Kim just shaded the man-of-the-match vote from midfield sidekick David Worrall, who further enhanced his blossoming reputation with an industrious performance in the engine room.
Mowbray rested quintet Jonathan Greening, James Morrison, Neil Clement, Paul Robinson and Ishmael Miller but handed new boy Scott Carson his second start.
Carl Hoefkens was given a run-out at centre-half while young guns Worrall and Graham Dorrans also made the XI.
Shots on goal were at a premium during the opening 15 minutes, with Roman Bednar's 20-yard drive, which deflected off ex-Wolves defender Gabor Gyepes and slipped just wide of the near post, the only effort of any note.
Northampton, who finished ninth in League One last term, didn't threaten the Albion goal until the 17th minute - but went mightily close to breaking the deadlock.
Midfielder Ryan Gilligan seized on a loose ball and rifled just over from 25 yards.
Four minutes later, Gyepes failed to get enough purchase on a header from Luke Guttridge's corner and the ball looped harmlessly wide.
Albion started to dictate the play as the half reached its midpoint and the lively Worrall was unlucky to see a 20-yard shot fly inches wide of the far post after a mazy right-wing run.
The Baggies' mini purple patch failed to yield a breakthrough goal and it was the Cobblers who threatened next, with striker Leon Constantine wastefully heading a great Jason Crowe cross well wide.
But the visitors were soon back on the attack and a moment of Kim brilliance in the 36th minute broke the deadlock.
After Bednar had been scythed down on the edge of the Town box, the 26-year-old curled a delightful free-kick over the wall and in off the left-hand post, giving keeper Mark Bunn no chance.
Albion soon piled forward again and Luke Moore saw a 25-yard grass-cutter fizz just wide of the far stick.
The final effort of the half came from Northampton striker Colin Larkin, who screwed his shot on the turn well wide from just inside the box.
Mowbray rang three changes at the break, with Carson, Jared Hodgkiss and Chris Brunt being replaced by Dean Kiely, Leon Barnett and Tininho.
Albion immediately put Town under pressure from the restart and centre-half Mark Hughes risked life and limb to get in the way of Barnett's goalbound shot after the hosts failed to clear a Marek Cech free-kick.
Northampton replied when left wing-back Liam Davis saw a cheeky 20-yard chip sail high over the bar.
Moore got himself into a good position in the box in the 50th minute but Hughes took the sting out of his right-footed curler and the ball trickled into Bunn's arms.
The game had finally come to life and Kiely was soon called into action, gathering Larkin's downward header from sub Andrew Holt's cross at the second attempt.
After Dorrans had fired a yard wide from distance, Bednar controlled Tininho's ball into the box and spun Gyepes in one movement, only to shoot straight at the grateful Bunn.
Albion got themselves in a defensive mess in the 57th minute and were relieved to see Constantine's acute 12-yard drive fly off Tininho and out for a corner.
There was a lull in the action - until sub Sherjill MacDonald burst into life in the 69th minute.
The former Dutch Under-21 international collected the ball inside his own half before surging past three Town defenders and firing just wide from the edge of the box.
MacDonald was at it again eight minutes from time when his trickery left Hughes on his backside, only to fire straight at Bunn from 18 yards.
NORTHAMPTON (3-5-2): Bunn; Gyepes, Hughes, Doig; Crowe (Holt 51), Osman, Gilligan, Guttridge (Henderson 76), Davis; Constantine, Larkin. Subs not used: Dunn, Dyer, Taylor, Coke, Jones, Dolman.
ALBION (4-4-2): Carson (Kiely HT); Hodgkiss (Barnett HT), Hoefkens, Pele, Cech; Dorrans (Elford-Alliyu 76), Worrall, Kim (MacDonald 60), Brunt (Tininho HT); Bednar (Beattie 60), Moore (Slusarski 60). Subs not used: Daniels (gk).
GOALS: ALBION - Kim (36).
BOOKINGS: None.
REFEREE: P Walton (Northamptonshire).
ATTENDANCE: 2,117 (627 away fans).
ALBION STARMAN: Do-heon Kim.
PIC: KIM'LL FIX IT...Do-heon is congratulated by his team-mates after scoring at Sixfields
