Peaty touched more than a body-length clear in 27.11 seconds, four-hundredths slower than his meet record semi-final time, to take gold on Sunday evening and add to his victory on Saturday in the 100m.
He said: “This week was about testing myself, which I feel I’ve done, and to come away having defended my British titles is a bonus considering I’m unrested.”
James Wilby, who claimed 200m success on Saturday, finished second ahead of Ross Murdoch.
Imogen Clark defended her women’s 50m breaststroke title and Freya Anderson was similarly successful in the 100m freestyle.
Leah Crisp triumphed in the women’s 1,500m freestyle and Jacob Peters claimed the men’s 100m butterfly title. Stephen Milne powered his way to victory in the men’s 200m freestyle final from lane one, while Alys Thomas led the field home in the women’s 200m butterfly.
Tom Dean completed a medley double when he took gold in the men’s 400m individual event having already won the 200m.
On Saturday, Yorkshire’s Lizzie Simmonds completed a backstroke double with victory in the 100m after already winning the 200m title in Edinburgh.
Simmonds finished ahead of German rivals Laura Riedmann and Lisa Graf in 1:00.65, with Scotland’s Kathleen Dawson winning British silver in 1:00.84.
Teenager Tom Dean secured his first senior British title with victory in the 200m individual medley.
Holly Hibbott defended her 400m freestyle title by winning her second gold. She was the first British swimmer home in 4:11.86. City of Sheffield’s Ellie Faulkner finished third.