Ben Brosnan rolled back the years with a crucial late goal which helped secure knock-out football for Wexford in the Tailteann Cup.
The 35-year-old substitute blasted a stoppage time goal and finished with 1-01 as John Hegarty's side locked down third position in the table with a 1-16 to 1-12 win.
Their reward is an All-Ireland preliminary quarter-final fixture next weekend while Leitrim are out after their third consecutive defeat.
Andy Moran's Leitrim, for whom Darragh Rooney top-scored with 1-04, will have deep regrets about their failure to convert a penalty with 20 minutes to go which would have put them four points ahead at that stage.
Instead, it was Wexford that pushed on for their first win of the competition with Brosnan's late goal moving them from three to six points clear.
Goalkeeper Darragh Brooks saved the penalty from Keith Beirne and also contributed three points from placed balls.
Both sides finished level on eight points in the National League though Wexford did beat Leitrim by 0-19 to 0-15 when the sides met in Round 5.
That result, and Wexford's draw with Fermanagh in Round 1 of the Tailteann Cup, which left them a point ahead of winless Leitrim in the table, left the Model County as slight favourites.
There was nothing in it for long spells though with the sides splitting 14 points evenly between them in the opening half to head in level on 0-07 apiece.
Wexford goalkeeper Brooks struck three of their points from placed balls while Rooney, who plays his club football with St Judes in the capital, registered the same amount for Leitrim.
But both sides kicked themselves for poor shot execution early on with Leitrim blasting five wides and dropping a number of point attempts short.
Wexford tallied the same amount of first-half wides and also winced as three great goal chances came to nought. Kevin O'Grady dragged a third minute shot wide and then cannoned a shot off the post just before the half-time. Conor Kinsella also fired wide after a fine run through the centre and lay-off by Robbie Brooks.
Leitrim's best goal chance in the opening half was a stinging drive from Tom Prior that goalkeeper Brooks tipped over.
Reigning Tailteann Cup All-Star Beirne, who missed the Round 2 loss to Fermanagh, returned to the lineup and booted two first-half points from frees, one off either foot.
Goalkeeper Nevin O'Donnell and defender Conor Reynolds were also recalled while Wexford made four changes from their last outing, drafting in Brian Cushe, Liam O'Connor, Dylan Furlong and Kinsella.
Leitrim piled on the pressure in the third quarter and carved out another goal chance in the 41st minute but Paul Keaney was thwarted.
Rooney eventually hit the net for them five minutes later when, after intercepting a Brooks kick-out, he started a lightning quick hand-passing move that ended with him palming in from close range.
That put Leitrim 1-08 to 0-09 clear and they should have had a second goal in the 49th minute when Beirne was fouled by Glen Malone for a penalty but Brooks dived low to his left to save brilliantly from Beirne.
Keaney drove the resulting 45 wide and Wexford, energised by the let-off, responded with three points in a row from Malone, substitute Brosnan and Paraic Hughes to take a one-point lead at the hour mark, 0-12 to 1-08.
It was anyone's game as an entertaining encounter drew to a conclusion and Wexford opened up a three-point lead entering stoppage time before finishing off a counter-attack with the Brosnan goal following great work in the buildup by the influential Hughes.
Wexford: Darragh Brooks (0-04, 0-02f, 0-02 45); Eoin Porter, Brian Cushe, Michael Furlong; Glen Malone (0-01), Alan Tobin, Mark Rossiter (0-03, 0-02f); Liam Coleman (0-01), Niall Hughes (0-01); Paraic Hughes (0-02), Eoghan Nolan (0-01), Kevin O'Grady; Conor Kinsella (0-01), Robbie Brooks, Dylan Furlong.
Subs: Ben Brosnan (1-01) for Kinsella 45, Conor Carty for Tobin 45, Brian Molloy (0-01) for Rossiter 55, Cian Hughes for R Brooks 68, Darragh Lyons for O'Grady 68.
Leitrim: Nevin O'Donnell; Cillian McGloin, Mark Diffley, Conor Reynolds; Aidan Flynn, Shane Quinn, Jack Heslin (0-02); Barry McNulty, Pearce Dolan; Darragh Rooney (1-04), Paul Keaney, Mark Plunkett; Tom Prior (0-01), Donal Wrynn, Keith Beirne (0-05, 0-04f).
Subs: Oisin McLoughlin for Wrynn 50, Conor Farrell for McGloin 52, Michael McKiernan for Prior 62, James Rooney for Heslin 63, Diarmuid Kelleher for Plunkett 68.
Referee: Paul Faloon (Down).
