England international Defoe, who will leave next month to join Major League Soccer team Toronto FC, came on with the game finely poised at 1-0 following Christian Eriksen's opener, and sewed up the three points for Sherwood's side with a measured finish.
"Jermain will score wherever he plays, in any league in the world," Spurs boss Tim Sherwood said.
"He is a goalscorer, he loves scoring goals and if he doesn't score he gets the hump. He will go home happy tonight.
"He warmed up like an Olympic athlete. I saw the appetite he was showing to come on and when he came on he showed his worth."