[2] At the age of four, Iafallo began skating but was held back from joining the local mite travel team for a year per his parents' request.

His father Tom, a restaurant owner and a coach, built a roller rink in their backyard for Iafallo and his sister Julianna to practice on.

[6] As the top scorer for the Regals during the 2010–11 Tier 1 AAA season, Iafallo helped guide the team towards a national championship.

[9] Having recorded 121 points in 152 games over the course of his four-year tenure with the Bulldogs, Iafallo was signed as a free agent to a two-year, entry-level contract with the Los Angeles Kings on April 19, 2017.

On May 7, 2021, Iafallo wore a letter on his jersey for the first time, serving as an Alternate captain after Dustin Brown was ruled out for the rest of the season with an injury.

On June 27, 2023, Iafallo was traded by the Kings, alongside Rasmus Kupari, Gabriel Vilardi and a 2024 2nd-round draft pick to the Winnipeg Jets in exchange for Pierre-Luc Dubois.