Cognitive abilities of animals are a focal topic in contemporary behavioral ecology and comparative psychology. Fish are the only vertebrate clade that is fully adapted to aquatic environments, and display distinctive adaptations in perception, information processing, and behavioral decision-making. The aquatic habitats on which they depend differ markedly from terrestrial systems regarding physical structure, light regimes, chemical cues, and ecological pressures. These differences have shaped the unique cognitive traits and behavioral strategies of fish. A systematic understanding of the cognitive performance of fish and the behavioral and ecological mechanisms underlying it explains the evolutionary trajectories and adaptive significance of animal cognition and provides theoretical and applied guidance for sustainable fisheries management, the optimization of aquaculture practices, improvements in the welfare of farmed fish, and informs discussions on ethical handling of animals. This review incorporates the research on fish cognition, emphasizing the advances in four domains: learning and memory, spatial cognition, perceptual discrimination, and social cognition. We further summarize commonly used experimental paradigms and methodological approaches in studies of fish cognition and, on this basis, critically assess the limitations and challenges of prior studies and priorities for future research. This study aims to deepen the theoretical understanding of fish cognition and broaden its practical applications in aquaculture and the management of fishery ecosystems.