The 33-year-old Denver, Colorado native beat out fellow designers Austin Scarlett and Michael Costello to take home the grand prize during Thursday night's finale.
> 'Project Runway: All Stars' recap: Finale - part 2
Neiman Marcus fashion director Ken Downing and designer Tommy Hilfiger had joined Angela Lindvall, Georgina Chapman and Isaac Mizrahi on the judging panel as the finalists showed their six piece mini-collections at New York City's Gotham Hall.
Guerra's collection, entitled 'Therapy', was inspired by the high levels of "insanity" he felt during the All Stars process and his subsequent channeling of his troubles into the clothing.
"Being on Project Runway: All Stars was the hardest thing I've ever done. I thought season 8 was hard, but this was leaps and bounds beyond difficult. Thank you so much!" he said following the win.
"I can't take anything for granted. I can't take what I've been given - I can't take my heart for granted. I have to celebrate it or it can be lost forever."
Guerra took home a prize of his own exclusive boutique in Neiman Marcus stores and on NeimanMarcus.com, a fashion spread in Marie Claire magazine and a position as guest editor for one year.
He will also receive industrial sewing machines and other equipment provided by Brother and $100,000 (£63,200) in equipment from HP, as well as a $100,000 cash prize from L'Oreal Paris.
Project Runway: All Stars airs on Lifetime.
> 'Project Runway: All Stars' recap: Finale - part 1
> 'Project Runway: All Stars' recap: Finale part 1