Christian Eriksen's early strike was cancelled out when Marcin Wasilewski headed home from a corner, before Shinji Okazaki put Leicester ahead within three minutes of his introduction as a half-time substitute.
However, we would have the final say as Harry Kane fired home emphatically from the spot in the 89th minute after Nathan Dyer was penalised for handball, taking the tie to a replay.
Spurs (4-2-3-1): Vorm, Trippier, Wimmer, Alderweireld, Rose (c), Dier (Bentaleb 68), Carroll (Kane 68), Chadli (Alli 73), Onomah, Eriksen, Son. Substitutes (not used): Lloris, Davies, Lamela, Winks.
Leicester (4-3-3): Schmeichel (c), De Laet, Wasilewski, Benalouane, Chilwell, Inler, Kante (Okazaki 46), King, Dyer, Ulloa, Gray (Albrighton 65). Substitutes (not used): Schwarzer, Drinkwater, Morgan, Simpson, Mahrez.
Goals: Spurs - Eriksen 9, Kane 89 (pen); Leicester – Wasilewski 19, Okazaki 48.
Yellow cards: Spurs – Bentaleb; Leicester – Wasilsewski, Schmeichel.
Referee: Robert Madley.