Evans (21) was part of a six-strong New Zealand team that travelled to Tokyo last weekend to compete at the Odaiba Cycle Festival.
The event was staged to demonstrate Tokyo's ability to host major cycling events, as the city is in the final bidding to host the Summer Olympics in 2020.
Evans won both the criterium event and the time trial in temperatures touching 35degC, with high humidity.
He said tactics had a part to play in his success.
''The first race I was in, an under-23 race, I ended up seventh and found it really hard, just with the heat and the tactics,'' he said.
''So, the next day I just thought I had to go out hard and make sure I was always handy. The attitude was to get out there and win it. I just had to be first around that last corner and then ride as hard as I could.''
The time trial, once around a lap that was just over 1km, started proceedings. Evans recorded the fastest time for the time trial of just over 50sec but his eye was on the main prize of a criterium win.
Racing over a mainly flat surface, Evans stayed handy to the front in the 40-strong field, which featured cyclists from all over Asia.
It came down to a bunch sprint of about 30 riders, and Evans won by a bike length from a couple of local riders.
He said it was a real thrill to win. He had to do it mostly by himself, as New Zealand team-mate Andy van der Heyden, from Timaru, suffered in the heat.
Lauren Ellis, of Mid Canterbury, won the women's event.
The New Zealand team had all its expenses paid as Tokyo authorities launch their final push to get the Olympics. The vote will take place next month.
Evans, a commerce student at the University of Otago, will mix the road and track this season. He is eyeing the omnium event on the track, with a possible tilt at making the Commonwealth Games team.
On the road, he is seeking to improve on his 20th placing in the Tour of Southland, which is raced in early November.
