In this study, Tamarix aphylla and Aerva javanica, plants used in folkloric medicine in the Asir region of Saudi Arabia were studied ethnobotanically, chemically, and biologically to assess their medicinal uses, phytochemical constituents, and biological activities. Ethnobotanical data were collected using semistructured interviews and the use values were calculated. A total of 61 informants were interviewed and results indicated high-value uses (0.9 and 0.7) for the plants. Phytochemical investigation indicated that the plants contained most of the phytochemicals that were tested for. The antioxidant activity was examined by assaying total phenolic content, 1,1-Diphenyl-2-picrylhydrazyl (DPPH), and hydrogen peroxide (H₂O₂) radical scavenging activity. .The bark extract of T. aphylla showed the best antioxidant effect in total phenolic content, DPPH, and H₂O₂ assays (278.02 ± 0.16 mg GAE/100 g; The half-maximal inhibitory concentration (IC₅₀): DPPH, 18.39 ± 0.62 µg/mL; H₂O₂, 252.94 ± 1.86 µg/mL), followed by extract of the A. javanica aerial parts (228.60 ± 2.09 mg GAE/100 g; IC₅₀: DPPH, 28.54 ± 0.53 µg/mL; H₂O₂, 154.17 ± 0.78 µg/mL) compared with ascorbic acid (DPPH: 27.27 ± 0.11 µg/mL; H₂O₂: 164.9 ± 0.37 µg/mL). The disc diffusion method performed for antimicrobial activity revealed weak activities in T. aphylla and A. javanica extracts (100 µg/mL) against six human pathogens. It was concluded that these plants possess therapeutic potential in the treatment of 18 types of ailments, which are important phytochemical constituents and antioxidant activities that justify their therapeutic uses in traditional medicine. Thus, this study laid sufficient background for further pharmacological research on extracts of these plants.