MOHAWk is a new method for direct observation of people’s behavior in urban spaces. It is an unobtrusive method of assessing physical activity and well-being, reducing the biases associated with self-reporting. It is suitable for urban spaces that generally have a small number of users, such as amenity green spaces, spaces that people pass through, such as green corridors, and spaces that have been validated in Europe. This method assesses three levels of physical activity (sedentary, walking, vigorous) and two other evidence-based well-being behaviors (connect: social interactions, take notice: attention to the environment) in urban spaces. Through three studies, we demonstrate that MOHAWk is reliable and valid from 112 h of observation in three urban spaces in Spain. MOHAWk can be used as part of more formal, institutionally-based research projects, and also as part of policy or practice (e.g. by local authorities or developers). This new tool is an inexpensive and easy-to-use method for generating data on the impact of well-being in relation to the urban physical or social environment. The results of 112 h of MOHAWk data, collected by four single observers at three different sites, suggest that MOHAWk is a reliable and valid observational tool for assessing physical activity and other well-being behaviors in small urban spaces.