The 35-year-old played 18 Tests for Australia and amassed over 10,000 First-Class runs for New South Wales and Tasmania.
"On behalf of the entire playing group, the ACA would like to extend its warm congratulations to Ed Cowan on his career, following his retirement this afternoon," Nicholson said.
"To represent Australia 18 times and being such a consistent performer in First-Class cricket are wonderful achievements of which he can be proud.
"One of the strongest supporters of the ACA, Ed has always put the interests of the wider playing group first, and has consistently advocated publically for the players throughout his career.
"I sincerely thank Ed for his contributions to cricket and for the support of the ACA.
"And I wish Ed and his family the best of luck.
"I'm probably most proud of the Shield titles I've been involved in and the Test wins rather than the personal achievements."