Weegar, Florida's seventh-round (206th overall) pick in 2013, recorded 12 goals and 47 assists in 61 contests for the Halifax Mooseheads of the Quebec Major Junior Hockey League. His 59 points ranked fourth among QMJHL defensemen.
The 20-year-old also registered 22 points (five goals, 17 assists) in 16 games this postseason.
"We are pleased to have reached a contract agreement with MacKenzie," Panthers general manager Dale Tallon said. "He is a young and mobile defenseman with an offensive upside, who will continue to grow and develop at the professional level."
Scouts note Weegar is a steady positional defenseman who possesses a strong hockey IQ and the ability to generate offense.