Exeter Chiefs were made to work hard by a determined Scarlets team at Sandy Park.
The Chiefs looked in total control after early converted tries from Ian Whitten and Simon Alcott.
But James Hanks' yellow card allowed Scarlets back into the match - with the visitors just seven points behind at the turnaround.
Scott Williams' try at the start of the second half levelled the scores, but the Chiefs won the game thanks to a Gareth Steenson penalty and a last minute James Scaysbrook converted try.
Elsewhere today, the Cornish Pirates won at Swansea by 30 points to 10 in the British and Irish Cup.
Kyle Marriott, Tom Bedford and Rob Elloway scored tries for the visitors.
Yeovil Town won for a club record 8th time in a row. Exeter City beat Accrington on Friday night, but Plymouth Argyle and Torquay both lost.
Exeter City picked up a club record tenth away win of the season. There were also wins for Yeovil Town and Plymouth Argyle.
Yeovil Town won for the fifth game in a row after a 3-0 win over Brentford. There were draws for Exeter and Plymouth, but Torquay lost 2-1.