The man became ill after being taken into police custody and later died in hospital.
A spokesman for the PIRC said:
"The Police Investigations & Review Commissioner has been instructed by the Crown Office and Procurator Fiscal Service (COPFS) to conduct an investigation into the circumstances leading up to the death in custody of a 24-year-old man.
"The man became ill after being taken to Falkirk Police Office on Monday 11 July 2016.
"He was then transferred to Forth Valley Royal Hospital in Larbert, but later died on Thursday 14 July 2016.
"A report into the findings of the investigation will be submitted to the COPFS in due course."