Dan Newton slotted three penalties but it wasn’t quite enough as the Warriors won 19-9 at a freezing Firhill.
A try from Jon Welsh and the reliable boot of returning fly-half Ruardih Jackson ensured the Scarlets missed the chance to climb into the play-off places.
The defeat leaves Nigel Davies’ men fifth in the RaboDirect PRO12 table while Glasgow climb to third.
The west Wales’ outfit’s woes were heightened following a serious-looking head injury to former Test prop Iestyn Thomas but, on a positive note, Josh Turnbull came through his latest return from a shoulder injury unscathed.
The Scarlets weathered an early storm and were unlucky not to take the lead after Gareth Davies sniped through. They instead had to settle for a penalty but Newton failed to convert.
Jackson was also off-target with the boot but handed his side a slender lead on 14 minutes before Newton equalised mid-way through the half.
David Lemi almost unlocked the Scarlets’ defence shortly before the half-hour mark after racing outside Jonathan Edwards but scrum-half Davies won the race to the ball to save a certain try.
The game was then held up following the serious-looking injury to Thomas and Glasgow quickly grabbed the opening try following the resumption of play. Ryan Wilson broke off the back of a scrum and Welsh powered over from close range, with Jackson banging over the conversion to hand the hosts a 10-3 half-time lead.
Jackson got the scoreboard ticking once again and stretched the hosts’ lead before Newton struck back for the Scarlets. The full-back continued to chip away at the Warriors’ lead before Jackson responded to restore Glasgow’s seven-point advantage.
Jackson slotted another penalty with 10 minutes to go and the Scottish outfit held on for a hard-fought victory.
