Objectives: Finding the best available evidence of efficacy and safety of oral collagen usage in improving the parameters of human skin. Materials and methods: The research was based on a search of the MEDLINE, CENTRAL and ClinicalTrials.gov databases using keywords "skin", "collagen" and "oral supplementation" with the use of Boolean operators. Clinical trials were found, which, based on the inclusion criteria, were either included in the study or excluded from it. An overall review of the included research was made. Results: The research included 12 randomized controlled studies in which 1013 subjects participated and in which the effect of oral preparations with collagen on skin parameters was examined. All 12 studies measured skin elasticity, and 11 found a statistically significant improvement in the parameter compared to placebo. Seven studies examined skin hydration, five studies found positive effects, and two found no significant difference in improvement compared to placebo. Six studies looked at wrinkles and all six reported a reduction of the parameter. TEWL reduction was examined in four studies, but it was not statistically significant in three. Three studies looked at skin roughness, and two showed improvement. Skin thickness was measured by two studies, one obtained an improvement in the parameter, while the other did not observe significant effects. Two studies reported a beneficial pore reduction effect. One study looked at the effect of collagen peptides on the level of natural moisturizing factors and saw an improvement in the group that was taking the higher dose. Conclusion: The evidence on the effectiveness of oral collagen preparations on skin parameters is limited due to the differences in the composition of the preparations and the inconsistency of the results of the reviewed randomized controlled studies. Therefore, a conclusion can be drawn about the positive effect of oral collagen administration on improving elasticity and reducing the appearance of wrinkles, while additional research is needed for other effects.