Wales, placed last in the last two Six Nations, put substance over style. Their six tries included three from lineout drives, one from a tryline ruck, one from an attacking scrum, and another stolen by Josh Adams.
Meanwhile, Fiji were restricted to three tries and Wales followed up their Six Nations success against Italy in March.
"We know how hard it is to face Fiji. It took us the 80 minutes to beat them," flanker Jac Morgan said. "But it was really important to get the win again to keep our momentum."
The Fijians blew away Wales in the first half, racking up 469 metres to Wales' 66, and 25 offloads to Wales' none. But their brilliance in front of a crowd of 16,456 at 33,000-seat Cardiff City Stadium wasn't underlined by points.
It cost Fiji, considered the home side and playing 16,000 kilometres from their real home to try to make some money.
From 10-10 at halftime, Wales scored two tries in two minutes through prop Rhys Carre and Adams, who chased a speculative kick into the Fiji in-goal. Fiji's Selestino Ravutaumada was nursing the rolling ball when Adams reached between his legs and touched it down for a try.
"I was just chasing really hard and I got quite lucky," Adams said.
Ravutaumada responded with Fiji's third try, a simple overlap, to trail by a point but Wales managed the last quarter well and scored in a lineout drive to replacement hooker Ryan Elias and from scrum ball to center Eddie James.
The first half was lit up by Fiji, marred only by a serious-looking leg injury to their former NRL star Semi Radradra.
Fiji scored within three minutes through flanker Pita-Gus Sowakula and somehow it was Fiji's only try. So often the last pass didn't connect.
Wales scored twice from lineout drives to Morgan, awarded player of the match after his first Test since a shoulder injury in November, and they went into the break remarkably tied on the scoreboard.
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