In this study, the antioxidant activity, phenolic content, and cytotoxicity of the above-ground parts of Maresia nana were evaluated using various assays. Antioxidant activity was assessed using the DPPH radical scavenging test, yielding an IC50 value of 90.55 ± 11.14 mg mL−1. The total flavanol content of the extract was 0.41 ± 0.01 mg QE/g, the total flavonoid content was 29.26 ± 1.88 mg QE/g, and the total phenolic content was 29.76 ± 2.64 mg GAE/g, indicating significant antioxidant properties and richness in phytochemical compounds. Additionally, GC-MS analysis identified eight bioactive compounds in the methanol extract of M. nana. The extract demonstrated 58.50 ± 3.5% cytotoxicity in A549 cells at the highest dose, while it increased proliferation in HEK293 cells, indicating selective cytotoxicity toward cancer cells. Furthermore, the binding affinities and interactions of two small-molecule ligands, Acridin-1(2H)-one, 3,4-dihydro-3,3-dimethyl-9-propylamino- and Androsta-3,5-diene-3,17-diol diacetate, with the Ras protein were investigated. Acridin-1(2H)-one showed a binding energy of −5.1 kcal mol−1, while Androsta-3,5-diene-3,17-diol diacetate demonstrated a stronger binding affinity with a binding energy of −5.5 kcal mol−1. In conclusion, the M. nana extract's antioxidant and phenolic profiles support its potential health benefits, and its selective cytotoxic effects on cancer cells suggest its promise for cancer therapy. Additionally, the binding characteristics of the ligands provide valuable insights for future drug development strategies.