The spatial analysis of the effects of marine and coastal tourism is a key tool for identifying the economic, social, physical, and environmental consequences of such activities in peripheral areas and for designing balanced development strategies. This study aims to spatially analyze the effects of marine and coastal tourism on sustainability indicators in the areas surrounding Chabahar County, Iran. The research is applied in purpose and mixed (quantitative-qualitative) in nature, conducted through a survey with a descriptive-analytical approach. Data were collected through documentary and field methods (questionnaire and observation). The statistical population consisted of Chabahar residents (236,200 people), with a sample size of 384 determined using Cochran's formula. Data were analyzed using one-sample t-test, Pearson correlation, and confirmatory factor analysis (SPSS, AMOS), spatial analysis based on remote-sensing imagery and ArcGIS combined with a Random Forest algorithm to assess the physical distribution of services, and the modified Leopold (Iranian) matrix to evaluate environmental impacts. Results indicate that marine and coastal tourism has had a significant positive effect on local economic prosperity (correlation coefficients up to 0.633) and social indicators (participation mean = 3.80), while physical development has been highly unbalanced and concentrated along the coastline: 92% of recent construction occurred within 5 km of the shore, the accessibility Gini coefficient reached 0.68, and Moran's I reached 0.82, leaving 47 villages without adequate access to basic services. Environmental assessment revealed an overall negative impact score of -1.3, underscoring the need for fundamental revision of coastal development policy. Adopting a spatial-justice approach to resource allocation, establishing secondary growth poles in the county's inland zones, and implementing environmental mitigation measures are therefore essential for achieving sustainable marine and coastal tourism development in Chabahar.