"We needed a keeper who has talent and Football League experience," the Northampton boss told the official club website after snapping up Nicholls to hopefully solve what has been a problem position for Town over the past year.
Nicholls is yet to feature for Wigan but impressed with Accrington during a 2011/12 loan spell.
Boothroyd added: "He is a good keeper, he did well at this level last season."