The Eurasian red squirrel is one of the species that has well adapted to urban habitats and is habituated to human presence. Its urban populations differ from those in rural habitats in terms of e.g. abundance, spatial organisation and behaviour. Food availability affects the ecology of red squirrels, so in this study we hypothesise that in the urban park with supplemental food, red squirrels will alter their activity rhythms to benefit from human presence. We therefore compared seasonal changes in the daily activity patterns of two red squirrel populations, inhabiting two different areas in Warsaw: a busy urban park (with plentiful supplemental feeding) and an urban forest reserve (closed for public). Between September 2018 and July 2019 we used camera traps to monitor red squirrels activity round-the-clock. In the park (contrarily to the forest), the number of records of red squirrels per 100 trap days was lowest in summer and highest in winter. Probably squirrels in the urban park, were able to maintain high activity during winter thanks to all-year-round availability of supplementary food. Daily activity patterns differed seasonally and between the study sites. In the forest they resembled those recorded in natural habitats, i.e. two activity peaks, one after the sunrise and second before the sunset. In contrast, park squirrels showed mostly one activity peak, beginning some hours after the sunrise and lasting until noon/early afternoon (depending on the season). Park squirrels were almost exclusively day-active, while forest squirrels were also recorded before sunrise and after sunset. We suggest that park squirrels shifted their activity to times with higher visitor frequency, which, assumingly, increased chances to obtain supplemental food.