With 16 scalps in five games, O'Keefe was the leading wicket-taker among spinners in the 2019-20 Sheffield Shield. He had also captained his side in 2011 and 2013.
The 35-year-old expressed disappointment over being overlooked for a new New South Wales contract. "I was disappointed when I was told that I wasn't getting a contract but I respect and accept the decision, so I have decided to retire from first-class cricket," O'Keefe said in a statement on Sunday.
"It's been such a privilege to play for my country and captain my state, but above everything else, I'm most proud to have played alongside some of the best blokes I've ever met. When I think about my time playing cricket, that's what I'll miss most," he added.
Meanwhile, O'Keefe will provide his services for the Sydney Sixers in the Big Bash League.The left-arm spinner finishes his Shield career with 224 wickets at 25.01 to his name.
He also represented Australia in nine Tests and seven T20Is. One of the highs of his red-ball career was when he returned brilliant match-figures of 12/70 against India in 2017, helping Australia set up a memorable Test win over in Pune.
He returned 6/35 in each innings of the Test, the best figures by a visiting spinner in a Test in India. Overall, he accounted for 35 Test wickets. (UNI)
