As socio-cultural concerns have gained currency in the sustainability discourse since the 1990s, facilitation of social cohesion has been emphasised as a precautionary measure to solve urban problems in distressed areas. In South Korea, as the tradition of social solidarity in residential communities has been substantially eroding, economically vulnerable groups have increasingly become helpless and hopeless. In order to suggest planning and management recommendations to improve the social cohesion of the impoverished communities, this study examined how the physical environment affects the social cohesiveness of the most disadvantaged public rental housing communities in South Korea. Four public rental housing estates in Seoul were selected for case studies. Based on the data collected by a questionnaire survey, interviews and field observation, the relationship among community cohesion, residents’ perception of the environment and their use of facilities in the housing estate and surrounding neighbourhoods was investigated quantitatively and qualitatively. The social cohesiveness of the public rental housing communities was assessed with the fourteen indicators in three dimensions. The dimension of ‘shared norms and trust’ was found to be the most evident, followed by 'attachment to housing estate' and ‘social networking.’ The level of social cohesiveness differed across the communities, and a community with stronger cohesiveness was found to be more active in community self-help and voluntary problem solving activities. The regression analysis proved that ‘shared norms and trust’ was affected by residents’ perception of housing block design, neighbourhood landmarks, educational facilities, residents' daily length of stay in the estate and their frequency of retail facilities use. Attachment to housing estate was influenced by residents’ perception of community facilities, retail facilities, educational environment, estate deterioration and spatial isolation. Social networking was affected by residents’ frequency in the use of retail facilities and public spaces, where diverse groups of people met. This study also identified the underlying factors affecting these relationships. Externally, the location of housing estates near commercial zones was significant. Internally, housing block arrangements creating more enclosed public spaces and attractive landscape, high quality welfare centres, regular maintenance and refurbishment of buildings, participatory revitalisation programs, community activities organised by welfare centres were found to enhance residents' perception and use of the facilities, thus improving community cohesiveness. In contrast, locations in areas with worn-out public housing estates, low quality retail facilities, poor ability of housing managers to organise surveillance and revitalisation programs, and residents’ low participation were adverse factors. With weakening collectivism but rising individualism, the traditional cultural influence on social cohesiveness has waned. Instead, good educational facilities in the neighbourhood, extensive use of public spaces, collective perception of poverty, incorporation of neighbourhood environment into estate environment and aspiration for good neighbouring are conducive to the community cohesion. Therefore, allocation of housing estates in the neighbourhoods with sufficient retail facilities, educational facilities and neighbourhood landmarks is suggested. More attractive housing block arrangements and the improvement of the retail facilities and welfare centres, consistent management of participatory revitalisation programs and more efficient investment in refurbishment of worn-out public housing estates are also recommended. / published_or_final_version / Urban Planning and Design / Doctoral / Doctor of Philosophy