Portugal is one of the major fish consumers in Europe and the World. According to the FAO and the WHO, fish consumption should be increasingly recommended in a healthy and sustainable diet, not only for the diversity of species but also for its health benefits to consumers. Fish is an essential source of nutrients, as it is low in fat content and high level of protein, vitamins, and minerals. In recent decades, this food group's consumption has increased and become available to consumers far from coastal areas. This study aimed to compare Atlantic Bonito samples captured in two seasons (Spring and Autumn) to characterise the seasonality of this specie regarding nutritional, chemical and sensorial properties. Parameters such as pH, water activity, moisture, protein, lipids, carbohydrates, chlorides, fibre, and ash were determined using the fish’s muscular tissue. A quantitative descriptive analysis (QDA®) was carried out with six semi-trained panellists. The fish attributes evaluated by the panellists were: characteristic colour, odour, and flavour; superficial shine; chipping; off-odour; ammoniacal and sea odour; hardness; juiciness; fibrousness; acid, bitter and sea/algae taste; and off-flavour. In order to compare not only seasonality but also the effect of the time during cooking, samples were divided into two batches: 5 and 10 min of cooking time. Results showed no significant differences in water activity, carbohydrates, chlorides, and fibre between fish fillets’ capture in Spring and Autumn (p?0.05). On the contrary, significant differences were found for moisture, protein, and ash between the fish fillets’ capture in Spring and Autumn (p>0.05). Regarding lipids content, Autumn fish samples were 6.32-fold higher than Spring fish samples (p<0.05). As for sensory analysis, panellists noticed some differences between Spring and Autumn samples regarding the following characteristics: superficial shine, chipping, characteristic odour, sea odour, hardness, juiciness, fibrousness, characteristic flavour, and acid taste. These differences were more pronounced on 10 min batch samples, regardless of the seasonality. The sensory analysis results showed that cooking time is the most important factor for the overall sensory evaluation regardless of the season. However, 5 min cooked fish fillets captured in Spring scored higher points than fish samples captured in Autumn. It can be concluded that the Atlantic Bonito seasonality influences sensory characteristics and nutritional properties, mainly the lipid content.