Many studies have demonstrated that xanthophylls, such as astaxanthin, have beneficial effects in human health, and their use in food supplements is thus encouraged. Moreover, such nutrients are frequently used in aquaculture to meet consumer demand for salmonoid flesh pigmentation. In this study different xanthophyll administration protocols were tested to verify pigmentation properties and safety of such mixtures of additives in trout diet. Residues of xanthophylls in muscle samples were determined by HPLC-MS/MS, reaching levels of 3.70 ± 0.04 mg/kg (astaxanthin) and 1.21 ± 0.06 mg/kg (canthaxanthin) during a 56 day administration period. On the basis of the average fish consumption in the human diet, the highest astaxanthin and canthaxanthin concentrations detected in trout fillets could result in weekly intakes of 1.63 and 0.53 mg, respectively, in humans; these values are not sufficient to achieve the positive effects described by many authors, but their residues could still represent an important source of carotenoids, alternative to the use of synthetic dietary supplements.