The Waldo County Sheriff's Office said the crash happened around 4:30 p.m. on the Albion Road.
A 46-year-old woman driving an SUV hit a lawnmower driven by Clement Blakney, 66.
Blakney was attempting to cross the street near Route 9 and Route 202.
His 5-year-old granddaughter was on the lawnmower at the time of the crash.
Both of them were taken to Eastern Maine Medical Center with life threatening injuries.
Blakney died early Thursday morning but his granddaughter is expected to be okay.
The driver of the SUV was also taken to the hospital with injuries that were not considered life-threatening.
There is no word yet on the cause.