The Blades were on course for a maiden win since their return to the Premier League after Gustavo Hamer fired them in front after 73 minutes in London.
A minimum of 12 minutes were added on at the end of the 90 and Spurs punished the newly-promoted side, with Richarlison levelling in the eighth added minute before Dejan Kulusevski grabbed a dramatic winner two minutes later.
Richarlison had been pictured in tears after being substituted in Brazil’s 5-1 win over Bolivia and revealed in midweek that he would seek “psychological help” following a turbulent time.
After scoring only once in the Premier League last season following his £60million switch from Everton last summer, Richarlison grabbed the leveller with a header from Ivan Perisic’s corner to set up a grandstand finish in N17.
Two minutes later and a slick team move ended with Richarlison teeing up Kulusevski, who fired through Jack Robinson’s legs to spark wild celebrations before Spurs captain Son Heung-min urged the Brazilian to soak up the applause at full-time.
“Richy was great,” Tottenham head coach Ange Postecoglou said.
“I thought all the subs who came on really helped, but that’s been a consistent theme.
“Yeah for Richy, I think it’s the point I was trying to make yesterday. For him to understand that you try and maintain a balance in life and his football hasn’t been that bad. He’s still been contributing for us.
“Sometimes when you struggle with certain parts of your life, you let it go into other areas, but the football is one area where he can control and he works hard every day in training and really got his rewards today.
“And hopefully that gives him a bit more of a settled feel to deal with the other areas in his life. For everyone, it’s about not letting it overwhelm you and hopefully a day like today helps him.”