"I understand that after a period of six months has expired, if I have complied with the conditions set forth below the charges will be dismissed," the New York Daily News quoted the actress as stating in an affidavit signed Dec. 19 and presented in court by her lawyer Friday.
"This is an important step in her rehabilitation," Bynes lawyer Gerald Shargel told the newspaper. "I am optimistic about her future and pleased with the result."
Bynes, 27, was charged last year with marijuana possession, evidence tampering and reckless endangerment after police said she threw a foot-long, glass bong out of the window of her Manhattan apartment.
Bynes has been living with her parents in California after months of inpatient treatment for bipolar disorder and schizophrenia.
The actress was arrested multiple times since April 2012 and has been accused of driving while intoxicated, hit-and-run and driving with a suspended license, in addition to the alleged bong-tossing offenses.
Bynes is the former star of the TV sketch comedy series, "The Amanda Show." Her film credits include "What a Girl Wants," "She's the Man" and "Hairspray."