Joyce Mitchell admitted on Tuesday to giving tools to the men, who broke out through tunnels under the prison.
Mitchell, 51, faces two to seven years in prison under a plea agreement.
Inmates Richard Matt and David Sweat were on the run for almost three weeks in June, setting off a massive manhunt involving hundreds of police officers.
Police shot and killed Matt near the Canadian border on 26 June. Sweat was later caught in the same area and sent back to prison.
Mitchell was a tailor shop instructor at Clinton Correctional Facility in Dannemora, New York. She was arrested soon after Matt and Sweat escaped on 5 June.
She told prosecutors that she hid the tools - including hacksaw blades, chisels and a screwdriver - inside frozen hamburger meat. The inmates were housed in a part of the prison where they were allowed to cook their own food.
Mitchell had also offered to drive the getaway car but backed out on the day of the escape, leaving the inmates to flee on foot.
The pair escaped through the prison sewer system after using the tools to break out of their cell. The escape set off a massive manhunt across northern New York and Vermont.
Although another prison worker has been charged in the case, authorities do not believe other plot extended beyond Mitchell and the inmates.
Matt was serving time for kidnapping and dismembering his former boss, while Sweat was imprisoned for killing a sheriff's deputy.
A former prison worker has pleaded guilty to charges that she helped two convicted killers escape from a maximum-security facility in New York.