The 27-year old made his debut for Ulster as a replacement against Border Reivers in April 2007 and has represented the province on 144 occasions, scoring 152 points.
He won his first cap for Ireland, against Canada, in 2009 and has won eight international caps so far, the most recent of which came in the win over Georgia at the Aviva Stadium last month. He has also represented Ireland 'A' 11 times.
Cave, who has been man-of-the-match in Ulster's last two home games, said: "I am delighted to be staying with Ulster until at least 2018. I have total faith in the coaching and management set-up we have and I am excited about what this group can achieve in the coming seasons.
"The support that we get, particularly at Kingspan Stadium, never ceases to amaze me and as someone who was brought up supporting Ulster, it's a pleasure to be involved for the next three and a half years."
Ulster's Team Manager, Bryn Cunningham, added: "Darren has been one of Ulster's most consistent performers over the last number of seasons. Aside from his considerable try scoring record, his defensive organisation is outstanding in what can be the most difficult channel to defend.
"His performance on Saturday, in which he scored one try and set up another, highlights Darren's importance to the squad. With undoubted interest from other quarters, we are delighted to retain his services for at least three more years."
Guinness PRO12
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