Background: Skin diseases represent a major burden in outpatient dermatology settings in Indonesia. The pattern of dermatological diagnoses varies substantially by age group and sex, reflecting differences in hormonal milieu, environmental exposures, and immune function. Objective: To describe and analytically assess the distribution of dermatological diagnoses stratified by age group and sex among patients attending in a private health and beauty clinic in Menteng, Central Jakarta, from January 2024 to December 2025. Methods: A cross-sectional, analytic observational study was conducted using secondary data from the clinic’s visit records. A total of 8,105 patient visits were included. Diagnoses were classified by ICD-10 code and stratified into eight broad age groups: Infants (<1 years), Young Children (1-4 years), Older Children (5-9 years), Young Adolescent (10-14 years), Older Adolescents (15-19 years), Young Adults (20-24 years), Adults (25–59 years), and Elderly (≥60 years). Chi-square (X²) goodness-of-fit was used for hypothesis testing. Results: Female patients predominated (74.9%; x2 = 2,016.761, p < 0.001). The most common diagnoses were acne vulgaris (n = 1,230; 15.2%), atopic dermatitis (n = 756; 9.3%), chloasma (n = 740; 9.1%). Acne vulgaris peaked in the Adults group (65.2% of all acne cases), chloasma in the Adults group (87%), and atopic dermatitis in the Adults group (34.9%). Chi-square analysis revealed that all top-10 diagnoses showed statistically significant non-uniform age distribution (all p < 0.001). Conclusion: Dermatological diagnoses at this private health and beauty clinic are age- and sex-patterned. These findings provide a basis for age-targeted prevention, early detection, and clinical resource allocation in urban private dermatology practice.