Satellite-derived nighttime light data, particularly products from the VIIRS sensor, have become well-established indicators for monitoring urbanization and socio-economic activities at national and regional scales. However, analyzing intra-urban dynamics at high resolution and within administrative units (municipal districts) remains a research gap. The present study aims to fill this gap by investigating the spatio-temporal patterns of nighttime brightness in the Tehran metropolis over a 12-year period (2014–2025). To this end, the monthly VIIRS time series was processed on the Google Earth Engine platform and analyzed using the Mann–Kendall test, Sen’s slope, hierarchical clustering, and Getis-Ord Gi* statistic. The results reveal a dual structure in the capital: a central core with high brightness and low growth rate (districts 6, 7, and 12), representing physical saturation, versus a dynamic periphery with accelerated growth, particularly in the west (District 22) and north (District 1). All districts, with the exception of District 19 (slope –0.37), exhibited increasing trends, and District 1 recorded the highest growth rate with a Sen’s slope of 1.6. The pattern of relative decrease or stabilization of brightness in 2020–2021, followed by a surge, is consistent with short-term events such as the COVID-19 pandemic. Hot spot analysis identified districts 6 and 7 as stable cores of nighttime activity and District 21 as a cold spot (dominated by open industrial land uses). Furthermore, the weak statistical correlation between population density and mean brightness, along with the inverse correlation between total population and brightness (r = –0.32), confirms the spatial mismatch phenomenon and highlights the functional distinction between commercial-administrative centers and bedroom communities. These findings demonstrate the capability of VIIRS data in monitoring physical dynamics, identifying growing or stagnating zones, and assessing environmental consequences such as light pollution, and will provide practical information for spatial planning and infrastructure management in the Tehran metropolis.