The 18-year-old striker joined Hibs' academy last summer and finished top scorer in the SPFL Under-20 League with 22 goals while scoring twice for the first team.
Cummings is now aiming to take the next step in his career under new head coach Alan Stubbs. "I love being here at Hibs, so extending my contract for another three years was an easy decision to make," he said.
"The past 12 months have been unreal for me - I've gone from working as a gardener to playing in the first team of one of the biggest clubs in Scotland.
"The jump has been big, but I'm confident I can now build on the start I've made and really kick on during the upcoming season.
"I've still got plenty to learn and I believe the coaches here will help me to develop into a better player."