Things You'll Need
Mice are nocturnal animals that often migrate indoors in search of warmth, food and shelter. Mice prefer to remain hidden, so they build nests in small, confined places such as inside lawn mowers. This may provide a scare for both human and mouse when you go to use the lawn mower. Moreover, if the mouse still is inside the lawn mover when it is turned on, it results in the mouse's needless demise. Fortunately, there are ways to get rid of mice and keep them away from the lawn mower.
Eliminate gaps and openings larger than 1/4 inch in the structure containing the lawn mower. This may be manageable if the lawn mower is kept in a small shed or garage, but more difficult if the lawn mower is kept in a barn. Exclusion is the most successful and permanent form of mouse control.
Caulk cracks and apply weather stripping around windows and doors.
Set traps around the lawn mower. If you find several mice in your lawn mower, consider setting up a multiple-catch mouse trap. The bait in the traps should override the desire of the mice to enter the lawn mower.
Place rodenticide inside the lawn mower.
There are humane traps available for purchase at most home improvement stores.
Rodenticide can be harmful and even fatal to pets and humans if consumed.