Wakefield were worn down by a crippling injury toll as they fell apart in the final quarter. The loss of Brad Drew, Jason Demetriou and Tony Martin, all with serious injuries, caught up with the Wildcats, who had led by eight points early in the second half.
Wakefield, showing several changes from the side that succumbed to Leeds last week, made a bright start when Scott Grix went over for a try inside the first three minutes of his debut for the club.
Harlequins' response was two tries in four minutes, the first of them from Scott Hill, carried off last week but capable of side-stepping his way over the try line this. The second was punishment for slack defensive work by the Wildcats, Chad Randall getting away effortlessly from dummy-half to set up Matt Gafa, Super League's leading try scorer, for his fifth of the season.
Wakefield seemed to have suffered another blow when the influential Drew went off with a suspected broken hand, but his replacement, Sam Obst, scored with his first touch, after Demetriou's superb pass put Grix through a gap. Danny Brough's second conversion put Wakefield ahead, ushering in a long period of pressure that Quins did well to withstand.
The Wildcats' frustration at failing to turn their possession into points intensified when a second key player, Demetriou, was carried off before half-time with a leg injury.
Wakefield overcame their setbacks when Danny Sculthorpe produced a quite magnificent pass out of the tackle to Jamie Rooney. Mark McLinden managed to catch him but Brett Ferris was there to finish the job.
Wakefield lost yet another player when Martin went off and David Howell had what looked a good Harlequins try disallowed for a forward pass. That was not too damaging because Randall scored almost immediately after Kevin Henderson surrendered possession near his own line.
Luke George's fumble under Hill's high kick set the stage for Ricki Sheriffe's try to put the London club ahead and Wakefield looked out on their feet when Henry Paul went over a couple of minutes later. Another high kick bounced kindly for Louie McCarthy-Scarsbrook to make absolutely sure for Quins but it was hard not to feel some sympathy for Wakefield's plight.
Harlequins: McLinden; Wells, Gafa, Howell, Sheriffe; Hill, Orr; Temata, Randall, Ward, Purdham, Mbu, Paul. Substitutes used: McCarthy-Scarsbrook, Rinaldi, Haggerty, Walsh.
Wakefield: Grix; Martin, Gleeson, Atkins, George; Rooney, Brough; Watene, Drew, Moore, Ferres, MacGillivray, Demetriou. Substitutes used: Sculthorpe, Obst, Henderson, Wilkes.
Referee: I Smith (Oldham).