BACKGROUND Recreational marijuana became commercially available in Washington State in 2014. Children with marijuana intoxication can have lethargy and altered mental status, often resulting in extensive workup. OBJECTIVE The aim of this study was to quantify the incidence of pediatric marijuana exposure before and after marijuana legalization/commercial availability in Washington State at a tertiary care children's hospital. METHODS Charts of patients 9 years or younger evaluated at a tertiary care pediatric hospital from October 8, 2007, to October 31, 2016, were retrospectively reviewed. Inclusion criteria were positive tetrahydrocannabinol urine toxicology screen and diagnosis consistent with unintentional marijuana exposure. Data included age, sex, exposure date range, symptoms, ancillary tests, consults, disposition, and marijuana source. Data were analyzed in R using descriptive statistics. RESULTS Seventeen unintentional marijuana exposures were identified during our study period, 8 cases before and 9 cases after legalization of recreational marijuana, which is 1.19 events per year in the 6.75 years before legalization compared with 3.88 events per year in the 2.32 years after (P < 0.05). Age range was 17 months to 7 years, with a median age of 21 months. Eighty-two percent received laboratory tests, 47% underwent head computed tomography, 6% underwent lumbar puncture, and 100% underwent social work evaluation. Thirty-five percent were discharged from the emergency department, 47% were admitted to general medicine, and 18% were admitted to the critical care unit. CONCLUSIONS Unintentional marijuana exposure incidence increased after legalization of recreational marijuana in Washington State at a tertiary care children's hospital. Providers should be aware of this increasing incidence. These data should be considered in the drafting of future marijuana legislation.