Cascarino, who now plays in France with Nancy, struck with a trademark header in the second half to clinch victory after Lithuania's Tomas Ziukas had replied to Cascarino's first-half strike with a thunderous equaliser just after the break.
The Irish have claimed second place in the Group barring a miracle for Lithuania, who must beat Macedonia away by 3-0 in their last match next month, and hope the Irish lose 10-0 at home to Romania.
The Irish will be without their leading player, Roy Keane, for the clash with Romania, who have long ago clinched top spot and automatic qualification. He was booked, for the second time in the qualifying campaign, for dissent.
Cascarino has now scored 18 goals in all, two short of Frank Stapleton's all-time Irish scoring record. His first last night arrived in the 17th minute. Keane found acres of space in the penalty area to get on the end of a long free-kick from the acting captain, Steve Staunton, and nod the ball across the six-yard box for the powerful Cascarino to come sliding in and knock it over the line.
Lithuania raised their game after the interval and, from a 52nd-minute corner, the ball bobbled off heads in the Irish penalty area and rebounded out for Ziukas to launch a right-foot drive through the crowded goalmouth into the top corner.
Cascarino missed two good chances to restore the visitors' lead - a diving header was clawed away by the goalkeeper Gintaras Stauce and another headed effort came back off a post - but, with 19 minutes left, he earned his reward. David Connolly was fouled and, from Staunton's curving free-kick from the left, Cascarino headed in at the far post.
LITHUANIA: Stauce (MSV Duisburg); Ziukas (VfL Leipzig), Kancelskis (Kareda Siauliai), Tereskinas (Stomil Olsztyn), Vainoras (Sokol Saratov), Skerla (Zalgiris Vilnius), Zutautas (Alania Vladikavkaz), Ivanauskas (Casino Salzburg), Mikalajunas (Kareda Siauliai), Preiksaitis (Torpedo Moscow), Narbekovas (Admira Wacker). Substitutes: Jankauskas (Torpedo Moscow) for Mikalajunas, h-t; Zvingilas (Harelbeke) for Preiksaitis, h-t; Slekys (Lugano) for Tereskinas, 76.
REPUBLIC OF IRELAND: Given (Newcastle); G Kelly (Leeds), Irwin (Manchester Utd), Harte (Leeds), Cunningham (Wimbledon), Keane (Manchester Utd), McAteer (Liverpool), McLoughlin (Portsmouth), Connolly (Feyenoord), Cascarino (Nancy), Staunton (Aston Villa). Substitutes: Babb (Liverpool) for McAteer, 83; Breen (Coventry) for Connolly, 89.
Referee: G Bikas (Greece).Reuse content