The MLS team released a statement on Saturday announcing Trent's passing.
"The Philadelphia Union is devastated by the heartbreaking passing of Holden Trent. While he was a wonderful player and fierce competitor, he was more importantly a devoted son, brother, fiancé, and teammate who made those around him better," the message read.
"He embodied the true meaning of determination, dedication and perseverance, and he will be deeply missed. We extend our greatest sympathies to his family, his fiancé, and his friends.
"Out of respect to Holden's friends and family, there will be no further statements at this time and ask that their privacy is respected as they grieve."
MLS Commissioner Don Garber added in a statement: "Major League Soccer joins the Philadelphia Union and our entire soccer community in mourning the tragic passing of Union goalkeeper Holden Trent.
"A young goalkeeper with a bright future, Trent showcased determination and professionalism every day as he contributed to the close-knit goalkeeping unit at Philadelphia.
"We extend our deepest condolences to his fiancée, his family and friends, his teammates and the entire Philadelphia Union community. MLS is coordinating with the club to provide players and family members with the resources and support they need during this tragic time."
Trent's passing comes just days after former Getafe and Marseille midfielder Abdelaziz Barrada passed away at the age of 35 from a heart attack.