Kane suffered the injury to his right ankle, and is the same knock as he picked up in September that ruled him out of action for seven weeks and 10 games.
Spurs are optimistic that the injury is not as severe this time after a scan on Tuesday, and he was able to walk immediately after the incident rather than being carried off on a stretcher.
“We can confirm that Harry Kane sustained ligament damage to his right ankle during Sunday’s FA Cup win against Millwall,” Spurs said on their Twitter account. “The injury is similar to the one suffered by the forward against Sunderland in September last year, however it is not considered to be as severe.
“Harry will continue to be assessed by our medical staff while he undergoes his rehabilitation at our Training Centre.”
It is unlikely Kane will be fit for the FA Cup semifinal against Chelsea, which is on the weekend of April 22 in just over five weeks, but he could return for league game against arch rivals Arsenal on April 30 — likely to be the final meeting between the clubs at White Hart Lane before it is redeveloped.
He will miss England’s friendly in Germany on March 22 and the World Cup qualifier at home to Lithuania four days later, as well league matches against Southampton, Burnley, Swansea, Watford and Bournemouth.