Phillips, who had scored twice in Sunday's first leg at Molineux, took his tally for the season to 22 - with six in the last three games - after a priceless 65th minute header as Albion ran out 4-2 winners on aggregate.
The former England striker rose unmarked at the far post to head home Robert Koren's left-wing cross and leave Albion one game away from an instant return to the Premiership and a £60million pay day.
It was a goal that had been coming as, for all their effort, Wolves struggled to produce the kind of form they are capable of.
Apart from one early thrust from Jay Bothroyd, Wolves' best chance to score came 60 seconds after Phillips struck when Albion centre-half Sam Sodje cleared the ball off the line after he misplaced his attempted clearance.
But it was a rare moment of anxiety for Albion who were inspired by the in-form Jason Koumas.
In contrast, Wolves' key-men, winger Michael Kightly and Andy Keogh, failed to fire.
The margin of their defeat would have been greater but for rookie goalkeeper Wayne Hennessey pulling off two impressive late saves from Koren and Diomansy Kamara.
With the stakes being so high, an edgy start was to be expected and the game only really came to life in the 12th minute when Wolves left-back Jackie McNamara blocked Zoltan Gera's goalbound shot following a pin-point Jason Koumas cross.
Wolves struggled to really test Albion and their best chance of the half went begging in the 17th minute when Bothroyd outpaced Sodje and Chris Perry only to see his shot smothered at the near post by Dean Kiely.
It was a move that sparked Albion into their best spell of the opening period and they should really have turned that pressure into a goal before the interval.
Koumas was the chief tormentor of Wolves as he gave Neill Collins a torrid time down the left wing.
But Phillips wasted a golden 22nd minute chance when he steered a Koumas cross wide when perfectly placed.
Koumas then had a shot blocked by Jody Craddock three minutes later before the well placed Kamara crashed his drive into the side-netting.
Koumas continued to dictate the play in the opening stages of the second half before Phillips made his decisive breakthrough.
Kamara picked out Koren and when his cross was missed by Gary Breen, Phillips made no mistake from just six yards.
All hopes of Wolves overhauling their two-goal deficit disappeared 11 minutes from time when Bothroyd blasted over the bar from close range.