Reymundo Perez, of Bancroft, was found guilty of first-degree reckless homicide and child abuse causing great harm, according to Stevens Point Journal Media. He was accused of slamming Felix Villa-Martinez to the ground twice on Oct. 26, 2011.
Perez did not appear to react Friday when Judge John Finn read the verdict.
Portage County Assistant District Attorney Veronica Isherwood played video during closing argument of Perez being interviewed by sheriff's investigators in which he implicates himself in the crime.
The jury rejected defense attorney Gary Schmaus' argument that Felix's mother, not Perez, had inflicted the child's fatal injuries.
The verdict concluded a nine-day trial. Perez could face up to 75 years in prison on both charges.
Attorneys will meet Monday to discuss a sentencing date.