During 2010–2011, varicella vaccination was an added requirement for school entrance in Wyoming. Vaccination exemption rates were compared during the 2009–2010 and 2011–2012 school years, and impacts of implementing a new childhood vaccine requirement were evaluated. All public schools, grades K–12, were required to report vaccination status of enrolled children for the 2009–2010 and 2011–2012 school years to the Wyoming Department of Health. Exemption data were analyzed by exemption category, vaccine, county, grade, and rurality. The proportion of children exempt for ≥1 vaccine increased from 1.2% (1,035/87,398) during the 2009–2010 school year to 1.9% (1,678/89,476) during 2011–2012. In 2011, exemptions were lowest (1.5%) in urban areas and highest (2.6%) in the most rural areas, and varicella vaccine exemptions represented 67.1% (294/438) of single vaccination exemptions. Implementation of a new vaccination requirement for school admission led to an increased exemption rate across Wyoming.