Davinson Sanchez put Spurs ahead against the run of play, and Christian Eriksen doubled the home side's advantage shortly after Jamie Vardy had missed a penalty for the visitors with his first touch after being introduced as a substitute.
The visitors will take the positives from an improved performance on Sunday afternoon, despite the defeat leaving the club 12th in the standings.
Spurs improved as the first half progressed, and Danny Rose should have perhaps done better from 12 yards out having cut inside onto his weaker right foot and fired an effort straight at Kasper Schmeichel.
However, that opportunity was not enough to discourage Leicester, who went straight back up the other end with James Maddison sending a first-time shot wide of the post after good work from Tielemans and Barnes.
Barnes then hooked an effort wide of the near post from inside the area after arguably being presented with too much time to make a decisive decision, and Spurs made him pay by taking the lead.
Eriksen was given the chance to cross the ball into the middle from the edge of the area and his delivery found Sanchez, who powered a header past Schmeichel from close range for his first goal in a Spurs shirt.
Lloris almost fumbled a Tielemans cross into his own net just before the half-time whistle, and it was a further let-off for the home side who would have acknowledged at half time that they were fortunate to be ahead.
Leicester continued to pose a frequent threat after the restart, but Demarai Gray sent a weak header straight at Lloris from 12 yards before doing the same with a shot on the turn.
The Foxes were then handed the perfect opportunity to get back on level terms with a penalty being awarded after Vertonghen clattered into Maddison inside the area.
Vardy was introduced from the Leicester bench in time to take the spot kick, but the club's top goalscorer saw his effort well saved by Lloris down to his right.
Things went from bad to worse for Leicester as Spurs doubled their advantage. Ricardo Pereira gave the ball away and, after linking up with Fernando Llorente, Eriksen fired a low shot into the bottom corner from the edge of the area.
Going two goals behind could have resulted in Leicester wilting during the final quarter, but Claude Puel's team found a second wind and the Frenchman was left with his head in the hands when Barnes failed to beat Lloris from no more than 10 yards out having been played in by Vardy.
However, Leicester did finally get on the scoresheet 16 minutes from time. Pereira's cross from the right was perfect for Vardy, who got across Toby Alderweireld to convert from close range.
Leicester remained on the front foot with Vardy drilling a half-volley over the bar, before fellow substitute Kelechi Iheanacho dragged a shot into the side-netting.
The Foxes would have been encouraged when four minutes of added-on time were signalled by the fourth official, but Son wrapped up the points for Spurs with a late third.
A clearance from Moussa Sissoko allowed Son to run clear on goal from before the halfway line, but the attacker had enough energy to remain ahead of Jonny Evans and fire the ball past a helpless Schmeichel.
TOTTENHAM HOTSPUR (4-4-2): Lloris; Trippier, Sanchez, Vertonghen, Rose (Walker-Peters 88'); Winks, Skipp (Alderweireld 71'), Sissoko, Eriksen; Son, Llorente (Wanyama 80')
LEICESTER CITY (4-2-3-1): Schmeichel; Pereira, Maguire, Evans, Chilwell; Ndidi, Tielemans; Ghezzal (Iheanacho 72'), Maddison, Barnes (Okazaki 88'); Gray (Vardy 59')
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