In the context of escalating environmental crises and the inadequacy of purely technical approaches, sociological studies increasingly emphasize the role of cultural factors in shaping sustainable behaviors. This study aims to examine the effect of ecological cultural capital on the environmental lifestyle of citizens in Sanandaj, drawing on Huber’s theoretical framework and Catton and Dunlap’s competing functions model. The research is descriptive-survey in method and applied in purpose. The statistical population consists of all citizens aged 18 and over in Sanandaj, from whom 384 individuals were selected using Cochran’s formula and multi-stage cluster sampling. Data were collected through a researcher-made questionnaire and analyzed using structural equation modeling. The validity and reliability of the research instrument were confirmed through confirmatory factor analysis and Cronbach’s alpha coefficient. The findings indicate that ecological cultural capital has a positive and statistically significant effect on environmental lifestyle. Among its dimensions, ecological beliefs show the strongest relationship with the waste management component, whereas objective cultural capital is at a lower level, and ecological knowledge does not have a significant relationship with environmental behavior, indicating the existence of a knowledge–action gap. Overall, the results suggest that the formation of a sustainable lifestyle is not merely the outcome of individual awareness but is influenced by a combination of cultural assets across cognitive, attitudinal, and instrumental domains. Therefore, achieving sustainability requires integrated approaches that go beyond awareness-raising and focus on strengthening deep-seated beliefs, developing tangible cultural infrastructures, and designing action-oriented educational programs.