Mourinho was relieved of his duties on Monday following a disappointing run of form which has seen Spurs drop out of the race for the top four.
Mason, the 29-year-old former Spurs and Hull midfielder who was forced to retire from playing in 2018, steps up from his role as head of player development at the club.
After joining the club as an eight-year-old, Mason played 70 times for Spurs between 2008 and 2016 before moving to Hull.
However, just six months into his stay at the Tigers he suffered a fractured skull that eventually forced him to retire 12 months later.
He returned to Spurs soon after in a coaching capacity and was named as the club’s head of player development in the summer of 2019.
Mason will face the media on Tuesday lunchtime.