The versatile youngster has impressed with the Under-18s since the beginning of last season, despite only becoming a full-time scholar this summer.
Usually deployed at right-back, Sandiford can also operate at centre-back, offering Tottenham flexibility across the defensive line as he continues his development.
The contract marks another milestone for a player who has already enjoyed success with the club's younger age groups. Sandiford helped Tottenham win the Under-16 Premier League Cup last season, starting the final against Fulham at Craven Cottage.
He has also made progress on the international stage, representing England at both Under-17 and Under-18 level.
Sandiford's leadership qualities have been recognised too. He captained England Under-18s to a 2-1 victory over South Korea earlier this season, adding another notable achievement to his growing experience.
The defender's journey at Tottenham began after he moved from Crystal Palace as a 14-year-old. His performances have since earned him a place in the Under-18 set-up and now his first professional agreement.
A boyhood Spurs supporter, Sandiford will hope the contract provides a platform for further progress as he works towards the next stage of his career.
His ability to play in more than one defensive position, combined with experience of youth international football and success in the Under-16 competition, gives him a strong foundation to build on.
Tottenham have congratulated the youngster on signing his first professional contract, with the next challenge being to continue his development and push towards senior opportunities.