A unanimous All-Ivy League First Team selection, Tretter was responsible for protecting quarterback Jeff Mathews' blind side at left tackle for last two seasons, allowing the Big Red to set new Cornell and Ivy passing records. Tretter was named an All-America third team member by both Beyond Sports College Network and The Sports Network. He was part of a line that allowed the passing game to pile up 3,748 yards in 2012, a mark that ranked third in the FCS. He started each of his final 20 games at left tackle and is the first offensive lineman to earn All-Ivy League First Team honors since Kevin Boothe in 2005.
Tretter is a converted tight end and a key reason the Big Red nearly cut its sacks allowed in half from 2010 to 2011, despite all of the passing attempts.
As a tight end, Tretter earned letters in his first two seasons at Cornell. He played in all 10 games as a sophomore in 2010, catching four passes for 62 yards and a touchdown on offense and making four special teams tackles. Tretter hauled in a 27-yard touchdown pass against Columbia, one of two catches of greater than 20 yards on the season.
He earned his first varsity letter as a freshman in 2009. Tretter is enrolled in the School of Industrial and Labor Relations.
Tretter, a three-year starter on both offense and defense, was named to the Class C all-state second-team as a senior at Akron HS. A varsity captain in both his junior and senior seasons, Tretter was named the team's MVP for both seasons, and the team's Most Improved Player as a sophomore. He was also honored as the Western New York Class C Defensive Player of the Year as a senior and was All-Western New York honorable mention. Tretter made the first-team all-league squad in all three of his varsity seasons. He was also a standout on the hardwood, graduating as Akron Central's all-time leading scorer and rebounder. A four-year starter and three-time all-league first-team selection, Tretter was named Western New York Player of the Year and to the All-Western New York third team as a senior.
Joseph Carl Tretter Jr. is the son of Joseph and Cynthia Tretter and has a sister, Katherine, who also attends Cornell. He also has three uncles who attended Cornell, including David Tretter 78, who lettered two times during a four-year football career for the Big Red.