As a 17-year-old, Iafallo garnered the attention of the USHL (United States Hockey League) when the left winger averaged just shy of a point per game with the U18 AAA Buffalo Regals. So much so that, that year the Fargo Force drafted Iafallo in the second round of the 2011 USHL Draft. From there, Iafallo made the team the following year and continued to turn heads with his play. In his two years with the Force, Iafallo racked up 95 points (45-50=95) in 127 games, including averaging over a point per game in the playoffs.
Iafallo's standout play in Fargo earned him a scholarship to the University of Minnesota-Duluth the following year. Consistently, Iafallo continued to impact the game and produce. As a freshman, Iafallo was named to all-conference (NCHC) freshman team, putting up 22 points (11-11=22) in 36 games. For the next three years, Iafallo helped lead Bulldogs to the NCAA Tournament, including a National Championship appearance in 2017 as a senior playing alongside the older brother of current Kings defenseman Mikey Anderson, Joey Anderson. That year, Iafallo also lead his conference, the NCHC in scoring, something his current teammate, Trevor Moore had done two years prior. In total, Iafallo recorded 121 points (48-73=121) in 157 games for Minnesota-Duluth.