Officials say 26-year-old Eric D. Griffin admitted in court that he fatally smothered his 4-week-old son in November 2010.
Griffin placed a pillow over the face of son, Nyir, removing the pillow once the baby stopped crying.
Police say when Griffin noticed his son was no longer breathing and left the home.
Nyir was later discovered unresponsive by his maternal grandmother.
The baby was taken to Lourdes Medical Center in Willingboro where he was pronounced dead.
Under terms of the plea agreement, Griffin will serve 12 years in a New Jersey State Prison for Aggravated Manslaughter.
Sentencing has been set for Feb.17.