Promoted Leicester survived a series of costly Tottenham misses either side of Pedro Porro’s first-half opener for the visitors at the King Power Stadium.
Vardy made Tottenham pay for their erratic finishing with a typically predatory header, capping his surprise appearance just days after he had been ruled out by Steve Cooper after suffering a pre-season injury.
The 37-year-old has now scored nine Premier League goals in 17 appearances against Tottenham, who trudged off wondering how they had failed to demolish Leicester during their dominant first-half display.
Tottenham finished fifth in Postecoglou’s first season following a campaign in which the Australian’s commitment to an all-out attack was eventually exposed at the cost of Champions League qualification.
Once again, Tottenham were hampered by poor finishing and unfocused defending.