Crayfish are consumed worldwide as a food resource. Red swamp crayfish (Procambarus clarkii) are not widely recognized as a food source, but signal crayfish (Pacifastacus leniusculus) are consumed in Japan. Because nutritional studies and information on red swamp crayfish are scarce, comprehensive comparisons of red swamp crayfish and signal crayfish are lacking. This study aimed to determine the nutritional value of red swamp crayfish as a food source by comparing pigments in the exoskeletons of red swamp and signal crayfish and by making a comprehensive comparison of their nutrients. The exoskeleton of red swamp crayfish is typically reddish-black, whereas that of signal crayfish is brown. A comparison of the exoskeleton pigments between the two crayfish colors using thin-layer chromatography showed bands corresponding to the ester and free forms of astaxanthin in all samples. The pigments in the exoskeletons of both species were the same regardless of body color. A comparison of the three major nutrients in the tail muscles showed differences in carbohydrates and fats between the two species, but the protein content was the same. It is assumed that this is due to differences in food composition and activity levels due to the habitat in which they grow. The fatty acid composition differed between the two crayfish. A comprehensive analysis of hydrophilic compounds in the muscles was conducted using triple quadrupole gas chromatography-mass spectrometry, which identified 107 common components in each sample, including various sugars, nucleic acid-related substances, vitamins, and functional compounds. Principal component analysis by GC/MS showed that the clusters of both crayfish species were largely divided between samples, reflecting the differences in their nutritional components. The presence of higher nutritional components in red swamp crayfish than in signal crayfish may lead to new applications regarding the potential use of red swamp crayfish as a food resource. This study demonstrates the significant nutritional value of red swamp crayfish and can be used to promote the potential use of red swamp crayfish as a valuable food resource and to expand the culinary and nutritional options in Japan.