Carlow led at half-time by 2-6 to 0-9 thanks to two well-taken goals by centre-half forward Craig Doyle.
Carlow were reduced to 14 men early in the second half when midfielder Jack Kavanagh was sent off but some fine saves by goalkeeper Kevin Keogh kept his side in front as Westmeath looked to take advantage of their extra man.
Westmeath finished the match strongly but despite dominating were unable to find the scores that would have forced extra-time.
Scorers: Carlow: C Doyle (2-4), D Kavanagh (0-3, 0-1 free), R Dunbar (0-3, all frees), P Keogh (0-2, all frees), E Nolan (0-1).
Westmeath: D Carty (0-5, all frees), A Mitchell (0-4, 0-3 from 65s, 0-1 free), A Devine (0-2), C Flanagan (0-1), B Lahart (0-1), D McNicholas (0-1), S Bardon (0-1), B Murtagh (0-1 from a free).
CARLOW: K. Keogh; A Corcoran; E Coady; E Kane; B Doyle; E Nolan; R Coady; R Dunbar; J Kavanagh; E Byrne; C Doyle; M Brennan; HP O’Byrne; D Kavanagh; A McDonald. Subs: P Keogh for R Dunbar (43), A Gaule for A McDonald (48), J O’Hara for A Corcoran (54).
WESTMEATH: P Burke; R Whelan; P Greville; E Price; D McCormack; A Mitchell; P Gilsenan; S Bardon; C Flanagan; C Curley; B Murtagh; D McNicholas; A. Devine; B Lahart; D Carty. Subs: J Shaw for C Curley (24), J Clarke for P Gilsenan (ht), N Flanaghan for D Carty (48), D Golden for B Lahart (53).
Referee: S. Cleere (Kilkenny).