Spurs have been busy on the transfer front this summer, having already signed no fewer than four new players.
A new right-wing back has been a priority for Tottenham boss Antonio Conte and Boro star Spence emerged as his top target.
Tottenham have been locked in negotiations with Middlesbrough for several weeks, seeing several offers being rejected, and the Yorkshire club were even getting frustrated that no breakthrough was being found.
However, Spurs have now made headway in their negotiations with the Championship club for Spence over a deal for an initial fee of £15m, which could rise up to £20m after add-ons.
And Tottenham are expected to seal a swoop for the defender before the end of the week.
Spurs are set to travel to South Korea on Saturday for their pre-season tour and Spence is in line to have a medical before that.
The 21-year-old also had several other suitors this summer, including Nottingham Forest where he spent last season on loan, but Tottenham are now close to winning the race for his services.
