The 39-year-old Serbian arrives in Switzerland after a mixed Asian swing, where he captured a record seventh China Open crown before suffering a surprise second-round defeat by Poland's Hubert Hurkacz at the Shanghai Masters, a tournament he has won a record four times.
Djokovic has endured an uneven season by his lofty standards. The former world number one exited the US Open in the first round, his earliest Grand Slam defeat since the 2006 Australian Open.
The decision to add Basel to his schedule comes as something of a surprise after Djokovic said following his early exit in Shanghai that he planned to play only the Paris Masters, scheduled for November 2-8, before the season-ending ATP Finals.
Basel offers Djokovic an opportunity to strengthen his bid for a 17th ATP Finals appearance. He sits 11th in the ATP Live Race to Turin and needs to finish inside the top nine, with world number one Jannik Sinner sidelined for the remainder of 2026 because of a persistent knee injury.
Djokovic will make his fourth appearance in Basel, having lifted the trophy in 2009 by beating Swiss great Roger Federer in the final.
He joins a strong field that includes Canadian Felix Auger-Aliassime and Americans Ben Shelton and Taylor Fritz at the ATP 500 indoor hard-court event, which runs from October 26-November 1.