Vassallo began marathoning immediately after graduating from Colby in 2007, representing the Central Mass Striders. He won the 2007
Maine Marathon in 2:26:54, which broke the previous course record. He was victorious again in 2012, lowering his course record to 2:21:12. In 2010, he won the
Philadelphia Marathon. Vassallo returned four years later to win the 2014 edition in a time of 2:17:28, which qualified him for the 2016 Olympic Trials Marathon in Los Angeles. At the 2018
Boston Marathon, Vassallo finished 10th in cold, wet, and windy conditions. Later that year, he ran a time of 2:17:27 at the
California International Marathon, which qualified him for the
2020 United States Olympic Trials (marathon) in Atlanta. Vassallo placed 100th of 235 men at the 2020 Olympic Trials Marathon on a hilly course through downtown
Atlanta. Following the
COVID-19 pandemic, he returned to marathoning at the 2022 Baystate Marathon in Lowell, MA, where he set a new course record time of 2:19:45. In the fall of 2023, Vassallo qualified for the
2024 United States Olympic Trials (marathon) with a 2:17:39 performance at the McKirdy Micro Marathon in Valley Cottage, NY. Despite dealing with an injury in the lead up to the Olympic Trials in Orlando, FL, Vassallo is one of 13 American men who finished the three
U.S. Olympic Trials marathons from 2016-2024. Vassallo was the top Masters finisher (age 40+) at the 2025
Grandma%27s Marathon with a time of 2:29:35. He was the ninth Masters finisher and 73rd overall at the 2025
New York City Marathon. ==Personal==