The Tottenham defender's curling shot - reminiscent of a David Beckham strike - flew into the top corner and sparked jubilant scenes among England fans who had packed pubs and fan-zones across the country.
The goal was followed by a series of chances for England as Croatia struggled with the pace of the Three Lions' attack.
Harry Kane hit the post with a rebounded shot at a tight angle after his first effort was saved by Croatia's goalkeeper Danijel Subasic.
Minutes earlier Kane had been left one-on-one with Subasic but put his strike wide, although he had been flagged offside.
Jesse Lingard also went close after finding space at the edge of the box but his shot crept narrowly wide.
Croatia edged back into the game near the end of the first half and defender Dejan Lovren felt he should have had a penalty on the stroke of half time.
Lovren got in a tangle with Harry Maguire in England's box following a free-kick but the referee refused to give a spot-kick after consulting with VAR.
England continued to look strong at the start of the second half and Kane nearly got on the end of a terrific cross on the volley by Trippier.
Raheem Sterling, who was a constant threat throughout the game, had a decent shout for a penalty after he appeared to be tripped by Domagoj Vida.
Soon after Kyle Walker bravely blocked a shot by Ivan Perisic that looked to be flying into the net.
Croatia drew level in the 68th minute after Perisic fired in a shot after a cross from defender Sime Vrsaljko - setting up a nervous final 20 minutes for supporters as they saw England's slender lead disappear.