Security chief Jean Laguel Civil is suspected of involvement in the plot that saw Moise killed at his home in the middle of the night by armed commandos who bypassed the president’s guards without firing a shot.
Civil has been placed in solitary confinement at a prison in Delmas, near the capital, Port-au-Prince.
“I can confirm that Jean Laguel Civil was arrested Monday by police as part of the investigation into the assassination of president Jovenel Moise,” police spokeswoman Marie Michelle Verrier told the AFP news agency.
Civil’s lawyer, Reynold Georges, also confirmed his arrest to The Associated Press news agency on Monday. He called his client’s arrest politically motivated.
It was not immediately clear if Civil had been charged with anything.
Civil joins more than 12 suspects the police have arrested.
Port-au-Prince commissioner Bed-Ford Claude had already ordered immigration authorities to prohibit four police officers who were responsible for Moise’s security from leaving the country.
Police on Monday also issued a warrant for Wendelle Coq Thelot, a judge for the highest court in the country who Moise had fired.
Details of the assassination remain unclear, but newly installed Prime Minister Ariel Henry has promised to bring Moise’s killers to justice.
Police have also arrested some 20 Colombian nationals as part of the plot they say was organised by a group of Haitians with foreign ties.