Christopher Gregor was charged with killing his 6-year-old son Corey three years ago in Stafford Township.
He was found guilty on Sunday of endangering the welfare of a child and aggravated manslaughter.
Surveillance video from 2021 shows Gregor repeatedly placing the boy on a fast-moving treadmill and him falling several times.
Corey died days later in the hospital.
Prosecutors argued that the incident left bruises on his body, which ultimately led to his death.
Gregor's sentencing is now scheduled for August.