He added an emoji with a victory sign in the wordless message.
The Seahawks retweeted a message from team owner Paul Allen that read: "@Seahawks Thank you @MoneyLynch for a great career as a Seahawk. So many memorable runs and quakes! #BeastMode !"
Seahawks cornerback Richard Sherman replied to Lynch's tweet by posting on Twitter, "Salute to my guy @MoneyLynch ... It was an honor sharing the field with you."
Seattle quarterback Russell Wilson tweeted, "Honor playing with one of the best running backs of all time! Going to miss sharing the backfield with you 24... #BeastMode @MoneyLynch"
Seahawks offensive tackle posted on Twitter, "@MoneyLynch for President"
Earlier Sunday, ESPN's Adam Schefter reported that the unpredictable Lynch people close to him he planned to retire.
Last month, Seahawks general manager John Schneider said Lynch "is leaning toward retirement."
Lynch struggled through an injury-plagued 2015 season with a hamstring issue and then abdominal surgery, playing in only seven regular-season games. He finished with just 417 rushing yards on 111 carries.
The 29-year-old returned for the NFC divisional playoff game against Carolina but had little impact during the Seahawks' 31-24 loss to the Panthers.
The five-time Pro Bowler would cost Seattle $11.5 million against their salary cap in 2016. By releasing Lynch, the Seahawks would save $6.5 million against the cap.
Lynch, who grew up in Oakland, Calif., and played college ball locally a Cal, was the Buffalo Bills' first-round draft pick in 2007. He played 3 1/2 seasons in Buffalo before he was traded to Seattle in October 2010 for fourth- and fifth-round draft picks.
In 127 career games (114 starts), Lynch gained 9,112 yards on 2,144 carries, an average of 4.3 yards per attempt and 71.7 yards per game. He ran for 74 touchdowns. He added 252 receptions for 1,979 yards and nine touchdowns.
Lynch helped guide the Seahawks to a Super Bowl win after the 2013 season, but he famously didn't get the ball at the goal line late last year's Super Bowl. Instead, Wilson threw an interception that sealed the New England Patriots' win.