The Tottenham forward starred for the Three Lions, with Wayne Rooney opening the scoring and Daniel Sturridge adding late on, while Dejan Damjanovic netted for the visitors.
Townsend set up Wayne Rooney for the opening goal after the teams played to a scoreless first-half stalemate. A Branko Boskovic own goal gave England a two-goal edge, before Dejan Damjanovic pulled the visitors back within reach.
Townsend provided a vital insurance goal with a wicked strike from outside the area, before Daniel Sturridge scored from the penalty spot in stoppage time to ice the victory that brings England to the top of Group H. With a win over Poland on Tuesday, England will win the group and cement a place in next summer's World Cup. At the very worst, England will participate in the playoff round of qualifying following Friday's result.
Defeat for Montenegro looks certain to have cost the nation a place at the World Cup, as second-place Ukraine is three points better off with a far superior goal difference.
As well as handing a debut to Townsend, England boss Roy Hodgson opted to pair Premier League top scorer Sturridge with Rooney in attack. Montenegro, meanwhile, was without captain Mirko Vucinic, defenders Miodrag Dzudovic and Marko Basa as well as midfielder Milorad Pekovic, but Manchester City striker Stevan Jovetic started, while also being handed the captain's armband.
With the backing of a vociferous home crowd at Wembley, England started brightly and created several half-chances before Leighton Baines did well to win the ball back and pick out Welbeck from the byline. The forward fired straight at goalkeeper Vukasin Poleksic at the near post, though.
Meanwhile, Townsend was causing all sorts of problems as he raced away down the right, before cutting in to shoot straight at Poleksic, who palmed the ball invitingly into Rooney’s path. Again, though, the striker could only fire into the side-netting from a tight angle.
But Rooney made amends for that miss just two minutes into the second half when he put England in front.
Unsurprisingly, Townsend was the architect, driving down the right before providing a cross that was headed into Welbeck’s path, and, although the onrushing forward’s shot was saved by Poleksic, Rooney was on hand to tuck the ball home from six yards.
England then doubled its lead in bizarre fashion after 61 minutes, when Welbeck raced into the box and fired the ball across the box before Boskovic, a former D.C. United Designated Player, toed the ball into the far corner of his own net.
Jovetic was unfortunate not to pull a goal back almost immediately, though, when his vicious right-foot drive from 25 yards out rattled the crossbar. The visitors did make a game of it with 18 minutes remaining when Damjanovic diverted Fatos Beciraj’s shot into the far corner.
England was not to be denied, however, and Townsend added a third with a fine right-foot drive from 20 yards with 12 minutes remaining, before Sturridge put the icing on the cake with a penalty in stoppage time. He was upended close to the byline by Ivan Kecojevic, and there was no stopping his composed spot kick as England left Wembley with a giant weight lifted.