Spurs made three changes as Lucas Moura, Erik Lamela and Kieran Trippier were recalled while the visitors stuck with the same XI that defeated Manchester City in the week.
The home side dominated the early stages although it took them to around the half-hour mark to have a first clear-cut chance, with Moura nodding Lamela's cross wide from six yards out while the Argentine himself nodded on to the bar soon after.
At the other end, Newcastle grew into the game as the minutes ticked by but lacked composure.
Arguably the best moment of the opening 45 minutes came when Moussa Sissoko guided a volley from a Christian Eriksen corner, but Martin Dubravka did well to save down to his left.
Into the second half and Newcastle almost opened the scoring with a fine header, but Salomon Rondon's effort cannoned off the post.
Spurs reacted by throwing on Fernando Llorente and the Spaniard had a headed effort wide from a Christian Eriksen, but his chances were compromised by him losing the ball in the sun.
However, he made amends on 83 minutes with the assist for Son's winning goal. Llorente controlled well to find the South Korean, who fired towards goal and it looked Dubravka's ball all day, but Jamaal Lascelles moved across him, potentially distracting the goalkeeper and the shot found the net.
Newcastle offered little else on the break and Spurs scrapped out a victory, in the process making it a record 29 Premier League games without a draw.