Twenty-one-year-old Alexander Stolte of Chelsea was sentenced on Wednesday.
He pleaded guilty in June to manslaughter in the death of 1-year-old Kyleigh McDaniel of Andover, N.H. in March 2010.
Stolte had been staying in Chelsea with family and babysitting when he slammed Kyleigh to the ground when she wouldn't stop crying.
He later called 911 when he found she wasn't breathing.
According to reports, for years, Stolte said he wasn't guilty. But weeks before his trial was to start, prosecutors obtained recorded phone conversations from prison in which he admitted slamming Kyleigh to the ground because she would not stop crying.
Stolte apologized to the court on Wednesday.