The turning point arrived after 34 minutes when, with the sides were level at 0-7 each, Waterford full-back Thomas O’Gorman was sent off after receiving a second yellow card.
These were just two out of a total of 14 yellow cards shown during a scrappy and disjointed 70 minutes.
Westmeath took advantage of the extra man to go in leading at half time by 0-9 to 0-7 and added a further five points after the break to lead 0-14 to 0-7 by the 40th minute.
Instrumental in Westmeath’s victory was the superb Dessie Dolan who scored some excellent points both from play and frees.
Westmeath still led by a seven-point margin heading into the final six minutes, 0-19 to 0-12, but surprisingly there was an exciting finish to this contest.
A goal by Waterford corner-forward Mark Ferncombe, when he finished to the net from close range at the near post, gave the visitors hope and when Tommy Prendergast added two late points the game was suddenly up for grabs.
Only a fine save by Westmeath goalkeeper Gary Connaughton, with his legs from Mark Ferncombe, denied Waterford the lead in injury-time.
With Westmeath hanging on, the home side broke down field and in the last action of the match Denis Corroon finished to the net to give Westmeath a five-point victory.
Scorers for Westmeath: D Dolan 0-10 (6f), P Greville 0-5 (5f), D Corroon 1-0, F Wilson 0-2, B Murtagh, C Jordan 0-1 each.
Scorers for Waterford: M Ferncombe 1-4 (0-3f), B Wall 0-5 (5f), T Prendergast 0-2, P Hurney, C O’Keeffe, K Cotter (45) 0-1 each.
WESTMEATH: G Connaughton; F Boyle, K Gavin, J Gaffey; C Jordan, A Finnan, D Harte; B Murtagh, D Corroon; F Wilson, David Glennon, P Sharry; P Greville, D Dolan, Denis Glennon.
Subs: S Quinn for P Sharry (54), T Warburton for Jordan (62), R English for Murtagh (65), R Doyle for Boyle (65), P Tormey for Doyle (inj. 69).
WATERFORD: K Cotter; Maurice O’Gorman, T O’Gorman, K Connery; W Hennessy, S Briggs, J Hurney; J Veale, B Phelan; B Wall, P Hurney, T Connors; S Fleming, T Prendergast, M Ferncombe.
Subs: T Grey for Briggs (inj. 10), C O’Keeffe for J Veale (ht), Michael O’Gorman for S Fleming (54), JJ Hutchinson for Connors (56), K Power for B Phelan (62).
Referee: Eamon O’Grady (Leitrim).