Dorian Harper, 58, pleaded guilty on Wednesday to three felony counts, including child abuse, assault and maiming.
Police said Harper, who was dating the child’s guardian, cuffed the boy to the porch in November 2013 as a punishment.
Wanda Larson, 58, was also arrested after deputies found the boy chained to the home in Union County.
A jury had been selected to hear the case on Tuesday.
Harper told the judge on Wednesday that he was sorry for his actions.
Larson, who faces similar charges, has pleaded not guilty.
She had been working as a supervisor at Union County’s Department of Social Services when she took custody of the boy. (Sky News)