The individuals were aged 70 and 78, and the incidents occurred at different times on Monday. The first singles match between Italian Lorenzo Musetti and Taylor Fritz was delayed, with an announcement made regarding a medical situation in the arena.
"The Italian Tennis and Padel Federation (FITP) and the ATP express their deepest condolences following the tragic passing of two spectators yesterday during the ATP Finals in Turin," a joint statement said.
"On-site medical and emergency personnel responded immediately, providing all possible assistance. Despite prompt intervention and subsequent transfer to hospital, unfortunately, both sadly passed away."
The season-ending championships have been held at the Turin arena since 2021, with the Italian city confirmed as host for 2026. The ATP Finals will remain in Italy until 2030.
Large crowds were at the arena on Monday, when, along with Musetti, Italian fans were out in force to cheer on defending champion Jannik Sinner, who defeated Canadian Felix Auger-Aliassime.