The deal is worth $45 million and included $20.5 million guaranteed, his agent confirmed. It also includes a $15 million signing bonus.
It marks the first move for new Panthers interim general manager Marty Hurney, who was officially hired Wednesday and immediately locked up a key cog on the O-line.
The deal makes Turner the third-highest paid guard in the league at $11.2 million a year.
Turner, 24, had one year left on his rookie deal. He has started 16 games each of the last two years and was a Pro Bowler this past season.