The shutdown comes 20 years after the launch of AIM, which became a wildly popular feature of AOL, the largest internet provider at the time.
Verizon, which acquired AOL in 2015 and merged it into a unit called Oath this year, said it is looking at new services to replace the instant messenger.
"AIM tapped into new digital technologies and ignited a cultural shift, but the way in which we communicate with each other has profoundly changed," said Michael Albers, vice president at Oath.
AIM has been overtaken by other messaging applications and social media amid a growing move to smartphones.
Facebook-owned WhatsApp and Facebook Messenger each have more than one billion users.
AOL has provided no specific user numbers but one report said fewer than 10 million people were regular AIM users.