The Ocean Health Index (OHI), which provides a new insight into the assessment of ocean ecosystems, has attracted wide attention recently since it was proposed in 2012. It has been applied to assess the oceans at the global, national and regional levels. However, the application of the OHI framework at the city level has not been reported yet. In this study, the feasibility of applying the OHI framework to assess the health status of the oceans at the city level was explored by a case study in Xiamen of China (Xiamen OHI). Xiamen OHI aims at assessing the current status of ocean health in the Xiamen City, but not comparing to other regional or international OHI cases. Large adjustments including setting goals, parameters and reference points were undertaken to customize the OHI framework to the city scale in Xiamen. The results showed the overall score for Xiamen OHI was 52 out of 100, ranging from 28 to 96 across different goals. Goals related to ecological factors including Clean Waters, Coastal Storage, Coastal Protection received very low scores; on the contrary, goals related to social and economic factors including Tourism and Recreation, Sense of Place and Coastal Livelihoods and Economies were scored high. The case study of Xiamen OHI indicates the feasibility of the application of the OHI framework at the city level after necessary adjustments, and the results can also direct to effective ocean health improvement in the future. This study thus contributes to promote the application of OHI framework at the local levels.