Narcan is a nasal spray that is used to reverse the effects of opioid overdoses caused by heroin and some prescription painkillers.
Walgreens said anyone who is administered the medication will be instructed to call 911 and seek medical attention after using it.
"By stocking Narcan in all our pharmacies, we are making it easier for families and caregivers to help their loved ones by having it on hand in case it is needed," said Rick Gates, Walgreens group vice president of pharmacy.
Naloxone, the drug contained in Narcan, is legally available without a prescription in 45 states.
Duane Reade stores in New York City are included in the plan.