The quality of the urban environment is affecting not only the well-being of inhabitants but also the sustainability of the urban environment and the ability of this environment to mitigate the effects of climate change. This paper aims to evaluate the effectiveness of the implementation of urban planning bylaws on the built environment quality in Palestinian cities. An analysis of a case study on a selected representative neighborhood in the city of Nablus is used as a method to address the current situation and to provide solutions for future urban development. The results from evaluating the level of the implementation of laws and bylaws highlight the very low level of implementation of urban planning regulation. The results show that most streets do not follow the planned street width, with limited pedestrian access and limited parking ability. Most buildings violate the setback and number of floors bylaws, which has resulted in bad street width-to-building height ratios and poor environmental qualities regarding view, sunlight entry, and ventilation. Green and public spaces, essential services, and parking lots are not sufficient, which will result in a challenge to future sustainability of the Palestinian neighborhoods. In order to achieve a sustainable urban environment, local authorities and municipalities can benefit from the assessment and the recommendation from this study to improve the urban environment.