Abstract: This invention relates to a lawn mower blade sharpener apparatus readily attachable to a bench grinder assembly having a rotating grinder wheel to sharpen an edge portion on a lawn mower blade. The lawn mower blade sharpener apparatus includes (1) a stationary grinder attachment assembly being clamped to an object support assembly on the bench grinder assembly; and (2) a pair of movable blade attachment assemblies, each connectable to an outer opposite end of the lawn mower blade. Each movable blade attachment assembly is provided with a main support rod engagable with the stationary grinder attachment assembly and having a plurality of blade connector clamps secured to an outer blade section of the lawn mower blade.