Dundubia nagarasingna (Distant) is a cicada (Hemiptera: Cicadidae) that has recently adapted to the tropical urban environments of Bangkok. There is little information on its phenology in the tropics and how its life-history traits have changed (or not) when the species adapts to urban environment. Synchronized emergence ensures mating success in cicadas. Short-term meteorological factors in the urban habitat may alter synchronized emergence patterns. This study investigated the intra-annual seasonal changes and longer inter-annual variations in the emergence pattern of a subpopulation of D. nagarasingna in an urban garden at the Faculty of Science, Mahidol University, Bangkok, Thailand, over 4 yr (2014, 2016, 2017 and 2018). The findings revealed that (1) the synchronized emergence of D. nagarasingna in the urban garden occurred annually from March to July with one clear peak in all 4 yr, (2) the seasonal activity pattern of adults in the urban environment has become longer than in the natural habitat, and (3) in certain years, air temperature and relative humidity could be used as predictors for cicada abundance. Our results emphasize that knowing the seasonal phenology of this tropical cicada species is important for planning efficient observation, which could reduce the cost of monitoring up to 72% and is essential for potential future understanding of responses to climate changes.