Peaty won his second gold of the championships in Kazan with victory in the 50m breaststroke final in a time of 26.51 seconds.
The City of Derby swimmer, who had set a new world record in advancing to final, then returned to the pool with Fran Halsall, Chris Walker-Hebborn and Siobhan-Marie O’Connor to win the mixed 4x100m medley in a world-record time of three minutes and 41.71secs.
Peaty finished strongly to touch first ahead of second-placed Cameron van der Burgh of South Africa (26.66s) and third-placed American Kevin Cordes (26.86) in the 50m breaststroke final.
It was Britain’s third gold in the swimming pool after Peaty won the 100m title on Monday night and James Guy won the men’s 200m freestyle on Tuesday, but a fourth was not long in coming from Peaty, Halsall, Walker-Hebborn and O’Connor.
“We fought for every inch there, as you can tell we’ve got nothing left,” Peaty told BBC2 shortly after Britain’s medley triumph.
“We left it all on the battlefield really and I’m just grateful to have a team like this and we can show the world that we’re good enough to do that. I give 100 per cent in training, 100 per cent in racing and I’m enjoying it.”
Peaty’s feat is all the more remarkable given that he was scared of water as a child – as his mother, Caroline, revealed earlier in the day.
“Adam wouldn’t sit down in the bath or stand under the shower. He just used to scream,” she told BBC Radio 5 Live.
“My friend then took him to go swimming as I couldn’t because it would break my heart as he would just scream. But after a week he got used to it.”
Elsewhere, Scotland’s Dan Wallace qualified fourth fastest for today’s men’s 200m individual medley final in a time of one minute 57.77secs, but Roberto Pavoni could not join him after finishing joint eighth and losing a subsequent swim-off with American Conor Dwyer.
“My 200 is always kind of my weaker event so it’s great to compete at the world stage in your second best event,” said Warrender swimmer Wallace, who will also compete in the men’s 400m medley competition on Sunday.
“It was a great opportunity to see where I was and see how I’m feeling and it gives me a lot of confidence for Sunday.”
Perth City swimmer Stephen Milne could not add to Britain’s medal haul, which currently stands at seven – four gold, one silver and two bronze – after he came home seventh in the men’s 800m freestyle final in a time of 7:49.86 – some 9.9secs behind winner Sun Yang of China. Lauren Quigley reached the women’s 50m backstroke final with a seventh-placed semi-final finish in 27.88secs, but Garioch’s Hannah Miley could not follow suit in the women’s 200m butterfly as she finished 14th in 2:09.21.
Meanwhile, Britain’s Gary Hunt took gold in the men’s high diving competition. Hunt, who claimed silver in Barcelona two years ago, went one better in Russia with a points haul of 629.30 from his five dives – more than 30 points ahead of second-placed Jonathan Paredes of Mexico (596.45) and third-placed Artem Silchenko of Russia (593.95).
The 31-year-old Englishman had established a 33-point lead going into the final round and clinched gold with a final dive which earned him 139.20 points.
Defending champion Orlando Duque of Colombia overcame sluggish performances in the early rounds to finish sixth thanks to a 151.20-point dive – the highest score of the final round.