The 25-year-old, a former Sullivan Upper pupil, has won three caps for Ireland, the most recent of which was an appearance off the bench against the All Blacks in last summer's tour of New Zealand.
He started the recent non-cap international against Fiji and scored a well-taken individual try in the 53-0 win at Thomond Park.
Commenting on the announcement, Cave said: "Signing this new contract with Ulster was probably the easiest decision that I have ever made in my life, especially at a time when the team have just won 12 competitive matches in-a-row.
"I honestly think that Ulster are going to win something between now and the summer of 2015 and I would never forgive myself if I wasn't around to be a part of that."
Ulster's director of rugby David Humphreys added: "I am delighted that Darren has committed to Ulster for a further two years. He is a highly dedicated player, who gives his all in both training and matches.
"Darren has been an important part of our success in recent seasons and the exciting thing is that his best years in an Ulster shirt are ahead of him."