Coastal and shelf regions play an extraordinary role with their rich marine resources and ecosystem services for human use. As an important transition zone, the Sea of Marmara (SoM) and its two narrow straits connect Mediterranean and Black Seas, and also support a diverse and rich ecosystem for many fish species. This chapter aims to examine the impact of fishing and climate change on the status of SoM ecosystem in the last two decades using landed catch and related common indicators. Results showed that the total catch dropped from a maximum amount of approximately 55,000 tonnes during the 2000s to 35,000 t in 2010s, and to 20,000 tonnes in 2020s. If the total catch in the 2000s is 100%, it was about 60% in 2010 and 35% in 2020s. Results of mean trophic level of landed catch confirm that there is a remarkable change in the catch composition during the last two decades. The values significantly decreased from 3.6 to 3.2 meaning withdrawal of predatory species such as European hake, turbot, and Atlantic bonito during 2000s, which led to the dominance of prey species such as anchovy, Mediterranean horse mackerel and deep-water pink shrimp in 2010s. The mean preferred temperature of the landed catch gradually decreased during 2000s and reached its minimum in 2011, followed by a slight increase and remained less fluctuated thereafter. Sea surface temperature gradually increased in the last 23 years and the average values were 15.8 ℃ in 2000s, 16.6 ℃ in 2010s, and 17.5 ℃ in 2020s. Results prove that the SoM is strongly influenced by external factors other than climate change alone, primarily overfishing. The continuous decline and overall negative values in fishing in balance index is related to declines in both the catch and the mean trophic level which indicates that fisheries are no longer efficient in the SoM. Although total vessel number decreased by its 1/4, landing-per-unit values did not show any increase, but gradually decreased after 2010, indicating stocks are declining and fishing effort are no longer sustainable as it is. Overall, ecological groups contributing to fisheries are mainly small pelagic fishes, followed by benthic invertebrates, and with a small number of medium pelagic and demersal fishes, and the SoM fishery depends on small pelagic fishes, mainly anchovy catch. It is concluded that the capacity of the SoM ecosystem has decreased significantly in the last decades and its ecosystem has become constantly vulnerable to human-induced pressures. Urgently, an ecosystem approach to fisheries management is required for understanding the ecosystem as a whole. Hence, specific recommendations for good environmental and fisheries management are provided at the end of this chapter. By implementing recommended measures, it is possible to enhance the resilience of the SoM ecosystem, safeguard its biodiversity, and ensure the sustainability of fisheries for future generations.