The 22-year-old Olympic champion, who had lowered the World Championship mark in qualifying, clocked 57.47 seconds- 0.34 outside his own world record.
The 22-year-old qualified fastest from the heats at the Duna Arena ahead of South Africa's Cameron van der Burgh (26.54) Brazil's Joao Gomes Junior (26.67).
"I'm very happy, I put in a 26.5 seconds [for the first 50m], then built off that on the back end".
"The 200m race felt so much better this morning, there was so much more control, I just feel more relaxed". I wasn't going out there this morning for a world record.
"Just planning it all out, making sure I know where I'm going at all times", Ledecky said.
Briton Ross Murdoch was eighth in 59.45 as Peaty retained the title he won in Kazan, Russia two years ago.
"It's 10am. It's quite early for a world record". "Last night gave me the confidence".
It has taken the Plymouth swimmer a little longer to take a global title, in his third world championships, but he paid tribute to trailblazer Peaty.
Britain's Adam Peaty set a world record of 26.10 seconds in the preliminaries of the men's 50-meter breaststroke at the world championships on Tuesday.
"That didn't really feel like my best race, so move it on tonight, pick up a few hundredths or tenths and we'll be very happy", he said.
Meanwhile, gold-medal machine Katie Ledecky cruised into the women's 1500m freestyle final from Monday's heats to stay on course for an historic 12th worlds gold.
Peaty's long-term goal is "Project 56", clocking under 57 seconds, and another gold at the Tokyo 2020 Olympics.
"He's given himself a four-year cycle to do that and it's important for people not to get fixated on that and lose sight of what he did last night, which is swim 1.2 seconds faster than anyone in the world has (done) in history", Furniss added.
Peaty made a strong start in Monday's final and nearly broke the 50m breaststroke record in the first half of the race.