Tanis Philomé was arrested in the Dominican Republic, the BBC reported. He has denied any involvement in the assassination of President Moïse on 7 July 2021.
Moïse was shot dead by gunmen who entered his home in Port-au-Prince.
Questions have been raised as to where his security team was at the time.
Haitian police allege a hit squad of mainly foreign mercenaries - 26 Colombians and two Haitian Americans - carried out the killing.
Bullet casings were found strewn across the ground around the property, but the only two people shot were President Moïse and his wife, raising suspicion that some members of the security team may have been in on the attack.
The president, who suffered 12 bullet wounds, died at the scene. His wife Martine was seriously injured but survived.
KI/PR