“Police officers apprehended and transferred the convict to prison,” the Tehran prosecutor’s office said, cited by the Fars news agency.
Baghai was sentenced in December to 15 years in jail for embezzlement and illegal business transactions.
He is very close to Ahmadinejad, serving as his deputy before becoming chief of staff during the populist former president’s second term.
The 48-year-old had been investigated for irregularities while in office and was imprisoned for seven months in 2015, although the reasons for this were never made public.
Ahmadinejad and Baghai both hoped to stand in the May 2017 presidential election, but the conservative-dominated Guardians Council rejected their candidacy.