Carotenoid plays a significant role in the nutrition and physiology of crustaceans. Crustaceans cannot synthesize carotenoids de novo but can metabolize and converse external carotenoid to meet the specific physiological and ecological adaptation needs during different stages. To date, research on the carotenoid’s nutritional requirements of crustaceans has primarily focused on the impact of adding astaxanthin to their diets on parameters such as growth performance, colouration regulation, antioxidant capacity, reproductive performance, immune function, and stress resistance. However, there is still limited understanding of the metabolic pathways and regulatory mechanisms of carotenoids within crustaceans. This necessitates further research to uncover these aspects. Building on the comprehensive analysis and summarization of studies regarding the composition and distribution of carotenoids within crustaceans, the types and sources of external carotenoids, the effective utilization of external carotenoids by crustaceans, and the nutritional requirements of crustaceans for external carotenoids, this article proposes a deeper exploration of the metabolic pathways of carotenoids within crustaceans. It suggests identifying the key enzyme genes involved in carotenoid metabolism and elucidating their biological functions. This approach aims to advance our understanding of the metabolism and regulation of carotenoids, which are essential conditional nutrients for crustaceans, and provide a scientific basis for efficiently utilising of external carotenoids in crustacean aquaculture.