Josh Sweeney joined the U.S. Marine Corps immediately after graduating from Ironwood High School in Phoenix. He earned the esteemed title of Marine Corps Scout Sniper and deployed with the 3rd Battalion, 4th Marines to Nowzad, Afghanistan. On Oct. 28, 2009, during his second deployment, Sweeney stepped on an improvised explosive device while on patrol, causing bilateral above-knee amputation. He also sustained serious injuries to his left hand and arm. Sweeney underwent dozens of surgeries during months of intensive rehabilitation. Sweeney received a Purple Heart for his sacrifice in combat.

During rehabilitation, Sweeney returned to his childhood passion for ice hockey. An able-bodied hockey player throughout middle school and high school in the Phoenix area, he was immediately drawn to sled hockey. From 2010 to 2013, he played on the San Antonio Rampage, a club Sled Hockey team composed entirely of injured military athletes. He also played for the Dallas Stars club team in 2012, helping the Stars earn the 2012 USA Hockey Sled Classic title.

Sweeney made the U.S. National Sled Hockey Team in 2011 and served as tri-captain during the 2012-13 season. The team won the 2012 IPC Ice Sledge Hockey World Championships in Hamar, Norway, and earned silver at the 2013 IPC Sledge Hockey World Championships. At the Paralympic Winter Games Sochi 2014, Sweeney played a pivotal role in securing gold for Team USA, scoring the game-winning goal in the final. In 2014, Sweeney received the inaugural ESPY Pat Tillman Award for Service, recognizing his military service and athletic achievements.

After his sled hockey career, Sweeney sought new athletic challenges. He began cross-training and competing in triathlons before discovering para Nordic skiing and biathlon after relocating to Idaho. The transition felt natural, as the mechanics of propelling a sit ski with poles closely resembled the movements of sled hockey. Sweeney competed in three cross-country skiing events at the Paralympic Winter Games Beijing 2022, with his best finish coming when he placed 16th in the men's sitting 18-kilometer race.

Sweeney shifted his focus to biathlon for the Paralympic Winter Games Milano Cortina 2026, leveraging his military background as a Scout Sniper to excel in the shooting component. During the 2025-26 season, Sweeney trained with Susan Dunklee, a three-time U.S. Olympian in biathlon, during development team camps. He earned multiple World Cup medals, including gold in the 1-kilometer sprint and silver in distance events.

Sweeney maintains an intensive year-round training schedule, incorporating swimming, hand cycling, wheelchair racing, weight training, and other cross-training activities to develop the endurance, power, and efficiency required for multiple Paralympic sports. Sweeney credits sport as a crucial part of his physical, emotional and mental recovery, providing him the opportunity to represent his country again and contribute to a team in meaningful ways.