Antonio's goal from Mark Noble's cross made it seven of West Ham's last nine home goals coming from headers, with the other two coming from the penalty spot.
Lucas Perez broke the sequence in the second half, scoring from open play with his feet to make it 2-1 to West Ham before Leicester's late equaliser.
For Antonio, it was his 15th goal in the Premier League to be scored via his head, out of 25 in total.
"Nobes put a great ball in and I made a great run and it just ends up on my head, like I’ve got a magnet on there!" Antonio told West Ham's official website.
His headed-goal ratio of 60 per cent is the second-highest for players who have scored at least 25 times in the competition.
Up next for Antonio and West Ham is a trip to Tottenham Hotspur on 27 April.