The expansion of digital commerce and the intensive use of social media have transformed how consumers search for information, evaluate brands, and make purchase decisions in the beauty market. This issue is particularly relevant to Somethinc because, despite its strong recognition as a local beauty brand, 2025 market data indicate weakening market share and sales performance. This study examines the effects of social media marketing and brand awareness on purchase decisions for Somethinc products among e-commerce users in South Jakarta, both partially and simultaneously. A quantitative survey design was employed. Using purposive sampling, the study involved 121 respondents who had purchased or used Somethinc products, lived in South Jakarta, and used e-commerce platforms. Data were collected through a Likert-scale questionnaire and analyzed using SPSS version 25 through validity and reliability tests, classical assumption tests, multiple linear regression, t-tests, F-tests, and the coefficient of determination. The results show that social media marketing has a positive and significant effect on purchase decisions (t = 3.438; p = 0.001), while brand awareness also has a positive and significant effect (t = 5.804; p < 0.001). Simultaneously, both variables are significant (F = 90.223; p < 0.001), with an R² of 0.605. Brand awareness provides the larger effective contribution at 38.9%, compared with 21.5% for social media marketing. These findings indicate that strengthening brand recognition and recall, supported by relevant and interactive social media activities, is an important combination for encouraging Somethinc purchase decisions in e-commerce settings.