Abrahams, who scored two goals in nine first team appearances for the O’s last season, has joined the Canaries for an undisclosed fee.
The 18-year-old will remain in E10 for this season however, following an agreement between both sides to loan the forward back to Orient for the 2017-18 campaign.
As part of the agreement, Abrahams will also be able to train with and feature for Norwich City’s U23 side.
Having penned his first professional deal in November 2016, Abrahams made his O’s debut as a substitute at Newport County on March 4 before scoring his first senior goal in a 2-2 draw at Luton Town on April 14.
Speaking on the move, Abrahams said; “Signing for Norwich is a great opportunity and what I believe to be the right move for my career.
“Orient is a Club that I will always hold close to my heart and I am extremely grateful for the help and support I have been given from such a young age.
“I was handed a fantastic chance last season in difficult circumstances, but the fans were so supportive during that time and I would like to thank them for that.
“I am pleased to be staying here on loan, and while I continue to wear the shirt I will give everything I have got to this Football Club.”