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In the last years, the demand for new eco-friendly ingredients has increased on the cosmetic market. Consumers are more aware of sustainable principles and, simultaneously, more conscious regarding the skin aging process. Chestnut (Castanea sativa) shells are a food by-product produced in high quantities in Europe. This waste has been described as a rich source of phenolic compounds with skin biological effects, such as antioxidant, antiradical, and anti-inflammatory activities. Despite the huge number of assays reporting the richness of chestnut shell extracts in bioactive compounds as well as the development of cosmetic formulations containing these extracts, no in vivo assays have assessed their clinical efficacy in human volunteers. The aim of this study was to evaluate the effect on skin face parameters of a formulation containing a chestnut shell extract in human volunteers (n = 22) who applied the product twice per day, for 56 days. For that, biophysical techniques, including Corneometer®, Cutometer®, and PrimosPremium, were employed, allowing the quantification of skin hydration and firmness, as well as of wrinkles’ depth and volume and wrinkles’ skin roughness. The results demonstrated that the formulation led to a slight decrease in roughness and wrinkles’ depth, although no significant differences with respect to a placebo were observed. In addition, a clear improvement of skin hydration was achieved (t0 = 54.00 Arbitrary Units (A.U.) and t56 = 58.62 A.U.). In contrast to the placebo, the active formulation increased skin firmness up to 31.76% in 50.00% of the volunteers, but without significant differences with respect to the placebo, probably due to the short period of treatment. A long-term use of the product is recommended to possibly observe significant differences in all parameters., This research was funded by the project PTDC/ASP-AGR/29277/2017—Castanea sativa shells as a new source of active ingredients for Functional Food and Cosmetic applications: a sustainable approach, supported by national funds by FCT/MCTES and co-supported by the Fundo Europeu de Desenvolvimento Regional (FEDER) throughout COMPETE 2020—Programa Operacional Competitividade e Internacionalização (POCI-01-0145-FEDER-029277). It was also funded by the projects UIDB/50006/2020 and UIDP/50006/2020 through national funds. This work was also financed by national funds from FCT—Fundação para a Ciência e a Tecnologia, I.P., in the scope of the project UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular Biosciences—UCIBIO and the project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy—i4HB. The authors are thankful to Sortegel for the chestnut samples and their availability during this work. The authors are thankful to Evonik for the samples. Ana Margarida Silva is thankful for the Ph.D. grant (SFRH/BD/144994/2019) financed by POPH-QREN and subsidized by the European Science Foundation and Ministério da Ciência, Tecnologia e Ensino Superior. Francisca Rodrigues (CEECIND/01886/2020) is thankful for her contract financed by FCT/MCTES—CEEC Individual Program Contract