More than two months after 85-year-old Chris Baghsarian was abducted from his home in Sydney's north in the early hours of February 13, police arrested a 19-year-old on Tuesday over two offences, including murder.
The man will face Mt Druitt Local Court on Wednesday.
Three others have already been charged and remain before the courts.
Mr Baghsarian's violent kidnapping shocked Australia after police revealed the widower was not the intended target and had been taken in a case of mistaken identity.
Police made several public appeals, urging the kidnappers to release the 85-year-old and return him to his family.
But on February 24, his body was found near a golf club in Pitt Town in Sydney's north west.
Police suspect the perpetrators aimed to abduct a relative of Sydney businessman Dimitri Stepanyan, who lived on the same street as Mr Baghsarian, with the hope of receiving a $50 million ransom.
Investigators believe Mr Baghsarian was killed on the night of February 14 at a makeshift stronghold in Dural, about a half hour drive from where his remains were found.
Mr Baghsarian's family described the harrowing ordeal as a nightmare, remembering him as a devoted father, brother, uncle and grandfather "who would never hurt a fly".