DeAngelo was selected by the Tampa Bay Lightning in the first round (No. 19) in the 2014 NHL Draft after he led all Ontario Hockey League defensemen with 71 points (15 goals, 56 assists) for Sarnia in 2013-14. DeAngelo signed a three-year, entry-level contract on Dec. 2, 2014.
On Jan. 8, 2015, Sarnia traded him to Sault Ste. Marie, where he finished the season with 89 points (25 goals, 64 assists), again leading all defensemen in the OHL. He won the award for top defenseman in the OHL (Max Kaminsky Trophy) and the Canadian Hockey League (Superstore Defenseman of the Year).