The 52-year-old from Leeds - who still competes on snooker’s main professional tour - beat David Lilley 4-1 in the final of the WAYS Facilities Management UK Seniors Snooker Championship in Hull.
Lines joins Jimmy White in being the only player to have won both the UK and World Seniors titles. Lines lifted the world crown in 2017.
“I’m over the moon to have won,” said world No 82 Lines. “I am just trying to enjoy myself out there. I want to play for as long as I possibly can because I just love playing snooker.
“When you get to my age and you haven’t won a ranking event, you accept that fact that you are probably not going to win one.
“So to win two prestigious events on the World Seniors tour, I’m really proud of myself. I am really honoured that I’ve done it.”
Lines came into the competition in good form, having reached the last 16 of the main tour’s UK Championship in York before Christmas.
Current World Seniors champion Lilley won the opening frame, but despite a 60 break in the second, Lines showed the battling qualities which have served him well over several decades as a professional player to pinch the frame on the black.
It spurred Lines on, as he won the next two frames to go 3-1 in front.
Lilley was again in pole position in frame five, but allowed Lines - who beat former world champion Ken Doherty in the semi-finals - back to the table, and the Yorkshireman produced a stunning shot on the red, down the cushion, on his way to a 47 clearance and the UK title.