Justina Di Stasio was first exposed to international competition at the 2011 Junior World Championships after she won the first of her back-to-back junior national titles. She was on the podium at the senior Canadian championships in 2012, 2013 and 2014 before winning her first senior national title in 2015. After winning gold at the 2014 Austrian Open, Di Stasio earned two more prestigious international victories in 2015 at the Dave Schultz Memorial and the Pan American Championships.  Di Stasio won 75kg silver at the Toronto 2015 Pan American Games, the same year she won the first of her three straight continental championships and competed at her first senior world championships. In 2017, she won 75kg bronze at the world championships. In 2018, after she missed qualifying for the world championship team in her natural 76kg weight class, she dropped down to 72kg and ended up being crowned world champion.