Mafileo attended Saint Kentigern College in Auckland and won the Auckland schools competition with them in 2012.
Senior career
Despite being named in North Harbour's squad for the 2013 ITM Cup, serious illness prevented him from making any appearances that year. He managed to make it onto the field the following season, but was merely a bit part player, playing 3 times. 2015 was when he really started to establish himself as Harbour's first choice in the number 3 jersey, he played 9 times that season, all of his appearances coming from the start. He continued to be a regular in North Harbour's Championship winning season in 2016, playing in all 12 of their games during the campaign and scoring his first ever provincial try as Harbour upset the more fancied and to win promotion to the Mitre 10 Cup Premiership for 2017.