Peter was born in Ottawa, Ontario in 1975. He was raised in Oakville, Ontario where he played amateur hockey in the Oakville Rangers system.
MacKellar was selected in the eighth round, 127th overall, by the Sault Ste. Marie Greyhounds in the 1992 Ontario Hockey League (OHL) draft, and won the Memorial Cup in his first season with the Greyhounds. In his third season, Peter was traded to the Owen Sound Platers, becoming an assistant captain in his fourth and final season during which he recorded 40 goals and 79 points in 59 games before being sidelined with a broken jaw.
Peter went on to play hockey at the University of New Brunswick, appearing in three Canadian University Finals in four years and winning one national championship. He then spent several years playing professionally in the United States with a number of teams throughout the mid-west and western regions.
Upon his return to the Durham Region, MacKellar was invited to tryout camp with the newly-resurrected Whitby Dunlops. He was selected to the team and subsequently named team captain, a title he would retain for 13 consecutive seasons. Over the course of Peter’s career, the Dunlops won several titles including consecutive Ontario championships (Robertson Cup) from 2005-06 to 2007-08 and advanced to the Allan Cup final in each of those seasons.
Included among Peter’s personal accomplishments is a 100-point season (51 goals) in 30 games during the 2005-06 campaign, along with many All-Star Team selections and his recognition by the Ontario Hockey Association (OHA) as Senior AAA Player of the Year in 2010-11. Over the course of his senior hockey career, Peter amassed 317 goals and 632 points in only 277 regular season games as well as 160 career playoff and Allan Cup points.
Peter is a dad to three sons, Baylan, Chayce, and Grayson. He currently resides in Courtice, Ontario and volunteers his time as a hockey, soccer, and baseball coach. He was also a volunteer firefighter in the Municipality of Clarington for 12 years.
He is the Manager of Marketing for Golf Ontario, and also has his own graphic design company; in his spare time, Peter often applies his artistic skills by painting on large canvases.