Solomon, who played eight seasons with the 49ers and three with the Miami Dolphins, succumbed after a battle with cancer, a statement released by the 49ers said.
Solomon played three season in Miami after being drafted by the Dolphins in 1975, and then was dealt to San Francisco, where he was a key cog in Coach Bill Walsh's West Coast offense.
Solomon finished his NFL career with 371 catches for 5,846 yards and 48 touchdowns.
"The 49ers lost a member of our family today. We'll miss you, Freddie Solomon. Our prayers go out to your family," 49ers President and Chief Executive Jed York said on Twitter.
"He inspired me to go out there every day and emulate him," ex-teammate Jerry Rice said in a statement released through the 49ers.
Solomon did volunteer work in the community following his retirement.