Its new 37g Milkybar Raisin & Biscuit bars will hit shelves on 26 July at an rsp of 52p.
Although Nestlé said Milkybars were already popular among mums, it claimed the £7m above-the-line marketing campaign would give all adults "permission to reacquaint with the brand".
The television campaign will kick off in August and feature a number of adults wearing a blond Milkybar Kid-style wig and blue spectacles and saying "Milkybars are on me!" to the camera.
In a bid to differentiate the product from the core Milkybar, targeted at kids, no children appear in the commercials, which finish with the new strapline 'Ungrow up'.
Getting the in-store location of Milkybar Raisin & Biscuit correct would be crucial, said Graham Walker, trade communications manager for Nestlé UK. "It is vital to locate the bar with similar need state adult products such as Aeros and Munchies," said Walker. "If retailers put it with kids' products they'll be missing a trick.
"Milkybar is one of those brands that people trust and grow up with but adults won't be expecting us to come to them."
The marketing strategy would use the advertising campaign for Nestlé's Rowntrees Randoms as a template, with two bursts of television and outdoor advertising in the summer and autumn and a constant digital presence, added Walker.