For the majority of the race, Wiffen stayed at the rear, but at the last turn, he caught up to Italy's Gregorio Paltrinieri and drove away to win in seven minutes 40.94 seconds.
Elijah Winnington of Australia came in second, more than two seconds ahead of the Irishman, who dropped to third place behind Olympic silver winner Paltrinieri.
Wiffen's victory occurred two months after at the European Championships, where they broke Grant Hackett's 15-year-old short course world record.
He was enjoying the applause at the Aspire Dome pool when he made a phone motion and banged it.
The 22-year-old with the beret stated, “Obviously, the goal going into this meet was to win a world medal and be on the top podium for Ireland.”
“It's the first medal Ireland has ever won at a global championship. I'm thrilled to say that, and it's just very amazing.”
Fukuoka's world champions from the previous year did not compete in the women's 200-meter freestyle, thus Haughey felt under pressure to win. She did it in 1:54.89, almost a full second faster than Erika Fairweather of New Zealand, who finished second.
Haughey, who took home silver in the 100- and 200-meter freestyle events in the Tokyo Olympics, told reporters, “It means so much to me, especially as the past few times, I've just missed out on the podium.”
“I'm the first [winner] from Hong Kong but hopefully there's more to come in the future.”
Haughey is the granddaughter of the late Charles Haughey, a three-term Taoiseach and former leader of Fianna Fáil.