Joseph Urquia pleaded guilty to third-degree murder Thursday under an agreement with prosecutors in the death of his daughter, Joselynn, in December.
Northampton County First Deputy District Attorney Terence Houck told the court Urquia said he punched her at least twice inside their Easton apartment because he was frustrated he couldn't console her.
The girl died two days later after suffering severe head injuries.
The 21-year-old Urquia was on probation at the time for an earlier assault charge. In that case he spanked another infant daughter so hard she bruised.
Houck says he'll seek a maximum sentence of 20 to 40 years. Sentencing is set for June 9.