The hard-fought victory in two hours, 41 minutes sends the Scot to just shy of eighth spot in the points race for the London season-ending finale which begins in three weeks.
Murray and Ferrer, the top seed and playing the event on a wild card like the Scot, were almost dead-level this week in the race for the last three places at the eight-man season wrap-up.
“It always feels great to win a title,” said Murray, who lost to Ferrer at the Shanghai Masters last week. “This was an extremely difficult match.
“He deserved to win the first set, I deserved the second and the third could have gone either way. I’m lucky I just managed to pull it off,” he said of a final set which featured seven breaks of serve.
Murray took victory when a serve was ruled an ace by electronic line-calling.
Ferrer still trails Murray by just a handful of points in the race to the season-ending showpiece, with both men now heading to Valencia for next week’s competition.
Novak Djokovic, Roger Federer, Rafael Nadal, Stan Wawrinka and Marin Cilic have already booked their places for London. -AFP