Justine Dufour-Lapointe started her young career during the 2010–11 FIS Freestyle Skiing World Cup. During that season, she became the youngest female winner of an FIS World Cup moguls event at the age of 16, winning the event in Mont Gabriel. She has two older sisters, Chloe Dufour-Lapointe and Maxime Dufour-Lapointe, who also compete in moguls. She won her first major medal the 2013 FIS Freestyle Skiing World Championships where she placed third, winning the bronze behind the dominant Hannah Kearney, who had won the gold medal. Dufour-Lapointe had fallen during her qualification but managed to place a second run good enough to qualify for the final. This was a proud result for Dufour-Lapointe; given the adversity required to win the bronze, she stated, "I’m so happy about my medal today, but in fact, it’s not the medal so much as the path that I took to get it. The path was tough but I made it." At the 2014 Sochi Olympics, Dufour-Lapointe competed in Moguls along with her sisters Chloé and Maxime. This was the fifth time that three siblings have competed at the Winter Games in the same event. Justine finished first overall in the event with a score of 22.44, with her sister Chloé placing second with a score of 21.66. With the result, she became the youngest freestyle skiing champion ever at the Winter Games. Thanks to the win, this earned the sisters' and Canada's first gold and silver medals of the 2014 Sochi Olympics. Dufour-Lapointe said of the event with her sister and her excitement that "Holding Chloe's hand meant that I wasn't alone. I was in shock. I saw Chloe and I felt calm. Holding her hand, I knew it would feel more like home." The 2015 FIS World Championships were another event to for Dufour-Lapointe to build her elite status. At these championships, she began by first winning the World Championship title in the mogul's event, of her win she said "My plan was simple. I wanted to find a balance between speed and technique. I stayed calm and focused during the day. I was really in a zone. To get the Olympic gold medal and now the World Championship gold medal is a dream come true. I’ve grown so much since the Olympic and learned a lot. That experience helped me here." She accompanied her gold medal with a silver medal performance in the dual moguls in Kreischberg, Austria. Dufour-Lapointe went in to the 2018 Winter Olympics as an underdog and having trouble finding the podium with her usual regularity. She would qualify for the finals and the third run against five other competitors for the medal. In the final run she finished in second place just one tenth of a second away from the gold medal. Dufour-Lapointe noted the distinction of her two Olympics saying "I feel so different than I was in Sochi. In Sochi, I was completely a kid, enjoying this life, not knowing what's going on around. But today... I know what to do, to focus on myself, my ski, my line, my moment, and that's all. Because if not, I won't be proud of me."
Personal life
Dufour-Lapointe is currently a student doing Cégep distance education in humanities. She is the youngest of three skiing sisters.