The show's premise revolves around general contractor Mike Holmes visiting homeowners (initially in the Greater Toronto Area in the earlier seasons, but also to various locales across Canada and the United States, starting with the seventh season) who are in need of help, mainly due to unsatisfactory home renovations performed by hired contractors.

Holmes would also go into detail to explain why the work he sees is substandard and needs to be replaced during the repair process.

[citation needed] Typically, after beginning the repair work, Holmes and his crew of contractors often find that their small repair project has escalated into a larger one due to surprises that they find and are forced to fix; only on rare occasions has the show's crew not been forced to tear everything down and start over.

Throughout the rebuilding process, Holmes often comments on the professionalism of the people hired for the job or lets other contractors talk about how to build things correctly.

On some occasions Holmes has vented out his frustrations with previous contractors' substandard work in front of the camera.

Particularly for projects involving new homes, Holmes often criticizes the developers for following minimum code and trying to save as many costs as possible.

The sixth-season Pasadena 911 two-hour episode also saw Mike and senior contractor Damon Bennett travel to Los Angeles to help out a couple in need after Holmes' own appearance on The Ellen DeGeneres Show.

During the seventh season, Mike travels across Canada to help homeowners in other parts of the country, although a number remain within Ontario.

Season seven is also notable for the formation of The Holmes Foundation, a charity organization affiliated with the show that promotes awareness of skilled trades (both to homeowners looking to hire them for renovations and to youth as a career choice), and its first project, the episode Lien on Me.