In this paper, the adverse effects of sea water environment on the fatigue life of woven carbon fiber/vinyl ester composites are established at room temperature. The fatigue life, defined as number of cycles to failure is determined for dry and sea water saturated composites. It is observed that the presence of sea water decreases the fatigue life of woven carbon fiber/vinyl ester composites, i.e., sea water saturation reduces the numbers of cycles to failure. The cycles to failure are comparable between dry and sea water saturated samples at lower strain ranges, but are drastically different at higher strain ranges. That is, the average measured reduction is between 37% at 0.46% strain range to 90% at 0.62% strain range. This implies that the influence of sea water saturation on the fatigue life is more pronounced when the maximum cyclic displacement approaches maximum quasi-static deflection. In addition, microstructural damage modes are identified at different stages of fatigue loading, where both dry and sea water saturated composites manifest similar damage modes that include, matrix cracking initiated near the top surface of the composites, progressive crack growth manifested as intralaminar matrix cracking, and specimen failure via fiber breakage. Due to the aforementioned reduction in flexural fatigue responses and damage mechanisms observed in woven carbon/vinyl ester composites exposed to sea water environment, special consideration is required while designing critical load bearing components in offshore marine applications for long-term survivability of structures. evaluation [4,5,6]. Often many structures are subjected to fluctuating and vibrating loads, typically categorized as fatigue loading, which are known to cause premature structural failure. This paper studies the influence of one particular load case, flexural cyclic loading (flexural fatigue), on woven carbon/vinyl ester composites under two different environmental conditions of dry and sea water saturation at room temperature.Fatigue phenomenon is characterized by the failure caused by repeated loading, which initiate and propagate cracks as loading cycles increase. These types of loads can be steady, variable, uniaxial, or multiaxial. The cyclic (fatigue) load levels needed to cause failure is often less than the maximum quasi-static load, making this an important parameter to consider during design. Synthesis, analysis and testing are necessary procedures to develop a product with durability [7] for fatigue design as fatigue failures in structures implicate huge costs. Fatigue testing methods and design criteria for FRPCs can be challenging due to the complex damage mechanisms, which can potentially cause large scatter in fatigue life data and correspondingly increase the challenges associated with fatigue-predictive modeling. Temperature and environmental interactions with fatigue loading further generate intricate manifestations of failure modes within the material. Particularly, understanding the fatigue behavior of high-strength carbo...