A woman has been charged over the death of a three-year-old boy north of Brisbane in June.

A second person has been charged over the death of a three-year-old boy north of Brisbane three months ago.

The woman, 34, has been charged with being an accessory after the fact to murder after being arrested on Thursday afternoon.

She will appear in the Brisbane Magistrates Court on Friday.

It follows the arrest of a 34-year-old man over a week ago. He was later charged with murder.

The toddler was found dead in a townhouse complex on Goodfellows Rd, Kallangur, on June 17 this year.

Last month, detectives appealed for more information from witnesses, saying they had two primary persons of interest.