Sun officials said they like Turner's toughness in the post.
"One of the things she's had to deal with in the pros is making the adjustment from power forward to small forward," Coach Mike Thibault said. "For us, we expect her to be a small forward. We've obviously made a decision to go with younger wing players, and she could fit into that plan. She still has to earn her spot, and we're going to give her that opportunity."
At UConn, Turner finished ninth on the all-time scoring list with 1,629 points, and was 10th all-time in rebounds with 797. She played on two NCAA title teams for UConn.
The Sun drafted Mahoney out of Kansas State in the 2005 draft. She's appeared in 49 games for Connecticut and averaged just under three points a game.
Terms of the trade were not disclosed.
Turner has been working out with former NBA coach John Lucas since the end of the 2007 season, and said she looking forward to returning to Connecticut.
"It's something that I wanted to be a part of for a long time. I've heard a lot of great things about Coach Thibault, and I watched the Sun play a lot, even when I was in college," Turner said.
The Sun's latest move comes two weeks after they traded All-Star forward Katie Douglas to Indianapolis for forward Tamika Whitmore, the 12th pick in the 2008 draft, and the rights to former Duke guard Jessica Foley.