Swansea were dealt a blow in the first half when Alvaro Vazquez left the field nursing a groin injury with the scores still at 0-0 and no recognised striker on the bench. However, winger Dyer was introduced and scored on the stroke of half-time to put the hosts ahead.
Mathieu Debuchy then inadvertently prodded beyond his own goalkeeper after the break before Jonjo Shelvey sealed all three points for the Liberty Stadium side, bringing an end to Newcastle’s four-match winning streak.
Boss Michael Laudrup made just one change to the Swansea side that lost 3-0 at Manchester City on Sunday, with Michel Vorm returning to the starting line-up in place of Gerhard Tremmel. Newcastle were unchanged from their 2-1 win against West Brom.
After an opening 10 minutes that was short of goalscoring opportunities, Yohan Cabaye went for an ambitious effort from just inside the Swansea half but was some way off target.
However, Vorm was called into action two minutes later when he got down brilliantly to his left to make a superb save from a Loic Remy header.
Vazquez – in the side due to injuries to both Michu and Wilfried Bony – had Swansea’s first chance of the match, blazing across goal from the right-hand side of the six-yard box.
Swansea then suffered a blow just before the half-hour mark as Vazquez added to the current Liberty Stadium attacking crisis by being forced off with an apparent groin problem.
He was replaced by Dyer and the winger was soon in the thick of the action, putting Swansea ahead shortly before the break. Tim Krul failed to deal with an Alejandro Pozuelo cross from the left and the substitute capitalised by smashing home from close range.
And Dyer could have doubled his tally just a minute after the restart, heading downwards from another Pozuelo cross, but straight into the arms of a grateful Krul this time around.
Shola Ameobi then turned well in the penalty area to force Vorm into a diving save shortly afterwards, before Swansea raced to the other end of the pitch and Shelvey rifled wide of the left-hand post.
Remy then had an effort blocked from point-blank range in the 58th minute as Newcastle claimed for handball against Ben Davies, but referee Howard Webb waved play on and replays suggested that the awarding of a penalty would have been harsh.
Swansea doubled their advantage in the 66th minute. Shelvey was sent clean through on goal, was too hesitant in applying the finish, but his blushes were spared as Debuchy inadvertently prodded the ball beyond Krul.
Shelvey then forced Krul into an acrobatic save from the edge of the penalty area in the 74th minute, but he had better luck nine minutes from time as he curled a superb effort past the Dutch goalkeeper to put the result beyond doubt.
