The 21-year-old didn't have long to savour the moment of revenge as he produced two careless passes that led directly to Liverpool taking the lead with goals from Daniel Sturridge and Victor Moses before half-time.
But he finished with a smile on his face after providing the assist that brought Michu's equaliser midway through the second half.
Shelvey's evening to remember brought an end to Liverpool's 100 percent start to the season, but the Reds still moved to the top of the Premier League table, one point clear of Arsenal and Tottenham, despite the end of their three-match winning run.
Reds boss Brendan Rodgers allowed Shelvey to leave Liverpool after three inconsistent seasons, so it was clearly a sweet moment when he gave Swansea the lead with less than two minutes played.
After making a hash of an attempted volley from long-range, Shelvey recovered his composure and surged away from Liverpool's new pounds 18 million (21.5 million euros, $28.6 million) centre back Mamadou Sakho before clipping a fine finish past Simon Mignolet after his first effort was blocked by Martin Skrtel.
It was the first goal Liverpool had conceded in the league this season and Shelvey celebrated wildly.
But within two minutes he was looking to the sky in dismay after his careless mistake gifted Liverpool their equaliser.
Picking up possession just outside his own penalty area, Shelvey flicked a woefully under-hit pass back to goalkeeper Michel Vorm without noticing the lurking Sturridge, who gleefully rifled home a cool left-foot finish.
Sturridge's sixth goal in five matches this season allayed any fears he would be short of sharpness after missing England's World Cup qualifiers against Moldova and Ukraine with a thigh strain.
And Sturridge went close to his second of the night when Vorm brilliantly kept out his header after good work from Moses unhinged the Swansea defence.
Liverpool had made their best start to a campaign since 1994-95 and they took the lead as Shelvey's match took another turn for the worse in the 36th minute.
Under no pressure, the midfielder played a dreadful pass straight to Moses and the punishment was instant.
Breaking from just inside his own half, Moses advanced at pace and, with Swansea's defenders backing off, he unleashed a powerful low shot that left the flat-footed Vorm rooted to the spot.
Swansea remained a threat and when Mignolet palmed Nathan Dyer's shot across the face of his unguarded goal, it seemed certain Wilfried Bony would turn in the loose ball, only for Skrtel to slide in with a superb last-ditch challenge.
Liverpool suffered a blow when Philippe Coutinho was forced off after a bodycheck by Ashley Williams left the Brazilian playmaker visibly wincing in pain.
And their frustrations grew even greater in the 64th minute as Swansea drew level.
Remarkably, Shelvey played a major role yet again as he finally provided an assist for his own team, timing his run to meet a through ball with a clever flicked header into the path of Spanish forward Michu, who slotted past Mignolet for his first league goal of the season.