The shy 24-year-old trains alongside fellow Kenyan Elijah Manangoi, 26, who was the 1,500 metres world champion until Cheruiyot took the title this year.
The pair's coach Bernard Ouma loves their "sibling rivalry", praising Manangoi's speed, Cheruiyot's endurance and their drive to outperform each other.
In the lead from the gun, Cheruiyot finished in 3 minutes 29.26 seconds, more than two seconds ahead of Algeria's Taoufik Makhloufi.
"I got the gold but it's not the end of everything," said Cheruiyot, whose new dream is next year's Tokyo Olympics.
The worst day of his career was in 2016 when he missed qualifying for the Rio tournament by half a second.
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The eldest of four siblings, he was born to tea and maize farmers in a west Kenyan village.
He started running to-and-from primary school, was competing at regional level by high school, but returned to the farm in 2011. Fortunately, friends encouraged him to keep running.
One was neighbour and local coach Jonathan Bellion, who developed a programme and pushed him to rest between races and eat a balanced died. "He taught me how to run," Cheruiyot said.
His preferred race at the time was the 800 metres.
At the 2014 trials for the World Under-20 Championships in Kenya, he had to finish in the top two to qualify, but came third, seconds separating him from his dream.
But the strong, 6-foot (183 cm) 18-year-old with a rugged run had impressed an onlooker – coach Ouma, who saw a future champion. "I decided, let me polish him and see how fast he can run."