The outdoor thermal comfort is one of the most important factors in creating the satisfaction and dynamics of a city’s open spaces. Various factors affect the outdoor thermal comfort of urban microclimates, and one of the most important of these is the geometry and layout of urban blocks. The purpose of this study was to investigate the influence of the common geometrical forms of urban blocks on the outdoor thermal comfort in cold climates of Iran. In this research, five common geometrical forms of urban blocks were selected as five different urban microclimates, and the effect of geometry of each form on the outdoor thermal comfort was evaluated in the cold climate of Hamadan city in Iran. To simulate the microclimate conditions and to evaluate the outdoor thermal comfort, ENVI software (ENVI-met) has been used as one of the most comprehensive simulation software packages for urban microclimates. The Predicted Mean Vote (PMV) is also used as one of the most comprehensive methods for estimating outdoor thermal comfort. The results of this study show the significant effect of mean radiant temperature and wind speed on the outdoor thermal comfort in the cold climate of Hamadan. In the five examined geometries, the courtyard house forms have preferable conditions for outdoor thermal comfort and the PMV index..