Wanting to play in a more football oriented program, he transferred to Mount Union College in the Ohio Athletic Conference.

While at Mount Union he led the team to two consecutive NCAA Division III Football Championships, falling just short of a third.

[4] During his sophomore season in 2005, he earned Ohio Athletic Conference second-team honors after having 68 receptions for 1,196 yards and 16 touchdowns.

As a junior, he was named to the Ohio Athletic Conference first-team and was the recipient of the Ed Sherman Award for the OAC's most outstanding receiver.

As a senior in 2007, Garçon was Ohio Athletic Conference first-team and was the recipient of the Ed Sherman Award, for the second time.

[8] During his time at Mount Union, he was teammates with future NFL wide receiver, Cecil Shorts III.

He displayed himself as a deep threat in Peyton Manning's offense, recording 47 receptions, 765 yards, and four touchdowns in his second season.

[25] Despite not playing for the entire second half of the game due to a foot injury, he finished with 109 yards on four receptions and one touchdown.

[27][28] In the Week 12 win against the Dallas Cowboys on Thanksgiving, he would score his second touchdown of the season after catching a 59-yard pass from Griffin III.

[31] In the Week 9 win against the San Diego Chargers, Garçon achieved a new career-high of 172 receiving yards in a single game.

[39] In the Week 7 win against the Tennessee Titans, after catching a short pass from quarterback Colt McCoy, Garçon ran the ball in for a 70-yard touchdown.

[42] After Jackson injured his hamstring in the Week 1 loss against the Miami Dolphins, Garçon moved into the WR1 position and quickly developed a strong trust with Cousins, due to his toughness when being hit along with a knack for finding the ball in traffic.

[45][46][47] In the Redskins' postseason matchup against the Green Bay Packers, Garçon posted five receptions for 70 yards in the 35–18 Wild Card Round loss.

[58] On December 11, 2018, Garçon was placed on injured reserve for the second year in a row after undergoing knee surgery.

[60] On February 14, 2019, the 49ers declined the option on Garçon's contract, making him a free agent at the start of the new league year.