Arin Kay Nesbitt, 50, changed her plea during a hearing Tuesday between Third District Canyon County Judge Bradly Ford.
Prosecutors agreed to drop 14 additional forgery counts and a computer crime charge in exchange for her guilty plea.
Nesbitt faces from one to 14 years in prison on each of the charges. She is scheduled to be sentenced May 28.
Nesbitt was accused of stealing an undisclosed amount of money from her Canyon County employer, the Southwest Idaho Resource Conservation and Development Council.
Nesbitt worked as a bookkeeper for the non-profit agency. She is accused of writing numerous unauthorized checks, forging authorized signatures and depositing the checks into her personal accounts at a bank in Emmett.
Authorities said Nesbitt concealed the thefts by altering accounting records. The thefts took place over a three-year period beginning in January 2010, Canyon County authorities said.
The Canyon County Sheriff's Office was notified by agency officials last August of their suspicions that Nesbitt was stealing from them. A two-month investigation led to charges against her.