Phil De Fries began practicing Brizilian jiu-jitsu at the age of 14, and worked as a drugs counsellor before becoming a professional fighter. Since the very beginning of his MMA career, Since his pro debut in 2009 De Fries has shown great submission skills, defeating the likes of Darren Towler and Stav Economou. After beating Stav Econiomou, Phil was then ranked the number 1 heavyweight in the UK and signed to the UFC.
De Fries was expected to make his debut against former British strongman Oli Thompson at UFC 138. However, Thompson had to pull out of the bout due to injury and was replaced by Rob Broughton. De Fries won the fight via unanimous decision
In his second UFC fight, De Fries faced Stipe Miocic on February 15, 2012 at UFC on Fuel TV 1. He lost the fight via KO in the first round.
De Fries then faced former strongman Oli Thompson at UFC on Fox 4. He won the fight via submission in the second round.
De Fries was then expected to face Matt Mitrione on December 29, 2012 at UFC 155. However, Mitrione stepped up to fight Roy Nelson at The Ultimate Fighter: Team Carwin vs. Team Nelson Finale and was replaced by Todd. De Fries lost via first round TKO due to punches.
Mitrione vs. De Fries eventually took place on April 6, 2013 at UFC on Fuel TV 9. He lost the bout via knockout in the first round.