The 18-year-old striker, who was born in south London and joined the club aged 10, has put pen to paper on a one-year deal.
"I'm thrilled to have become a pro at Millwall," he told the club website.
"I know there is still a lot of hard work to be done now, but I'm confident in my ability and if I can keep progressing with the development squad and score a few goals, hopefully I can break into the first-team squad here.
"I'm grateful to the coaches at Millwall who have helped me along the way and to some of the first-team lads, like Paul Robinson, who have given advice and done some coaching with us. It will be great to be training with them on a regular basis and, who knows, playing alongside some of them one day."