Background: Chickenpox (varicella) is an acute viral respiratory infection transmitted from person to person through airborne droplets. It is characterized by a typical vesicular rash affecting the skin and mucous membranes. Varicella is highly contagious, with secondary attack rates ranging from 61% to 100% among susceptible household contacts. Goal: This study aimed to compare the incidence and epidemiological characteristics of chickenpox in Uvurkhangai province before, during, and after the coronavirus disease 2019 (COVID-19) pandemic, as the incidence has exceeded the national average in recent years. Material and Method: A total of 1,804 chickenpox cases registered in Uvurkhangai province between 2017 and 2024 were obtained from the H-Info surveillance database. The study period was categorized into three phases: pre-pandemic (2017–2019), pandemic (2020–2022), and post-pandemic (2023–2024). Data were analyzed using Microsoft Excel, ArcGIS, and RStudio to compare temporal, demographic, and geographic patterns. Result: The incidence of chickenpox in Uvurkhangai province decreased 2.7-fold during the pandemic compared with the pre-pandemic period and increased 1.8-fold in the post-pandemic period. Before the pandemic, the highest proportion of cases occurred among kindergarten-aged children (2–4 years). During and after the pandemic, school-aged children (5–9 years) accounted for the largest proportion of cases. Across all study periods, the highest numbers of cases were reported in the densely populated soums of Arvaikheer and Kharkhorin. Significant changes in age distribution and socioeconomic characteristics were observed compared with the pre-pandemic period (p < 0.001). Chickenpox cases were most frequently reported during the winter and spring seasons. Conclusions Chickenpox cases are most common among school- and kindergarten-aged children in the densely populated soums of Arvaikheer and Kharkhorin, particularly during the winter and spring seasons. Strengthening surveillance and implementing targeted preventive measures in schools and kindergartens are essential to reduce the risk of future outbreaks.

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