The 17-year-old has progressed through the Black Cats' academy ranks and broken into the Under-21 squad over the past year, impressing for both the Under-21 and Under-18 sides during that time at the Academy of Light.
On signing his first contract, Cowan said: "I'm over the moon to sign this contract. I've been here around 10 years, so it's amazing to have signed it. I want to say thank you to everyone who has helped me, because the coaches and my family, I wouldn't have been at this moment if it wasn't for them."
Head of Academy John Hewitson praised the goalkeeper's development and urged him to keep working hard as he takes the next step in his career at the club.
"We are really pleased that Joe has committed his future to the club," Hewitson said.
"He has been at the academy for a long time and a lot of staff members have contributed to his development, and to see him progressing so well is really nice to see. Joe knows that this is only the beginning and there is a lot of hard work to come in the future."
Cowan has already established himself as the Under-21s' first-choice goalkeeper, having been fast-tracked through the age groups at the Academy of Light in recognition of his rapid progress as a young stopper.
Sunderland's academy has a strong recent record of developing goalkeepers who have gone on to feature for the first team, with the club long regarded as a reliable pipeline of talent between the posts down the years on Wearside.
The club will hope Cowan can follow a similar path in the years ahead as he continues his progression through the ranks, with further recognition likely to follow if his development continues at its current rate under the club's coaching staff.