The father in Perth is accused of killing his own baby, found with broken bones, had an assassination killing.
Dylan Clinton O'Mara, 23, was charged after his seven-month-old son Shussui was found dead in his hut at their home in Rockingham in April 2016.
But prosecutors rejected the case at the Supreme Australian Supreme Court on Thursday, saying there was no reasonable possibility of conviction.
Outside the court, Defense attorney Nick Serry said O'Morea now wants to grieve for his son.
"He will forever be broken because he can not attend the funeral of his son," said Sherry.
Mr O'Mara also wanted to thank those who believed in him, said the lawyer.