McCardell caught 883 passes, 13th on the NFL's career list, over 17 seasons. He had his most productive stint in six seasons with the Jacksonville Jaguars (1996-2001), but he spent his final year as a player with the Redskins, catching 22 passes for 256 yards in 2007.
The Redskins selected McCardell in the 12th round of the 1991 NFL Draft out of UNLV. However, he spent his rookie season on injured reserve for a team that won Super Bowl XXVI.
"Keenan is an outstanding addition to our coaching staff," Shanahan said in a statement released by the team. "He has all the attributes that you look for in one to become an outstanding coach in the National Football League. Keenan has instant credibility with our players as someone who played in this league for 17 years, won two Super Bowls and played in multiple Pro Bowls. He will be able to pass along much of the knowledge and expertise he picked up throughout a great career."
This is McCardell's first full-time coaching job in the NFL. He completed a Bill Walsh Minority Coaching Fellowship with the New York Giants during training camp in 2009 and last month coached receivers in the East-West Shrine Game.
League sources told NFL Network's Jason La Canfora last week that the Tampa Bay Buccaneers also were interested in McCardell for their receivers coach job. McCardell played two seasons with the Bucs (2002-03) and helped them win Super Bowl XXXVII.
The Associated Press contributed to this report.