Acacia seyal and Adenium obesum are used in traditional medicines by indigenous communities of the Asir region of Saudi Arabia. The present study aimed to acquire the phytochemical profiles, quantify the trace element contents and the total phenolic (TPC) and flavonoid (TFC) contents, and evaluate the antioxidant activity of the two species. Phytochemical screening was conducted to detect the presence of the phytochemical constituents. Bark samples were digested with a microwave, and ICP-MS was used for the elemental analysis. The antioxidant capacities in DPPH, HO, and FRAP assays and the TPC and TFC were determined by spectrophotometry, and their correlation with the IC of the DPPH and HO and the EC of the FRAP capacities were analyzed by Pearson's correlation. Both plant extracts contain a variety of phytochemicals. A. obesum had the highest concentrations of all 11 elements measured. In both plants, manganese was found at the highest concentration, and cadmium exhibited the lowest concentration. The aqueous-methanolic extract of A. seyal showed the highest TPC (309.32 ± 2.15 mg gallic acid equivalent/g), whereas the aqueous-methanolic extract of A. obesum exhibited the highest TFC (32.16 ± 3.16 mg quercetin equivalent/g). Significant differences in the IC and EC values were observed among the tested plant extracts. The highest antioxidant activity was found in aqueous-methanolic extract of A. obesum. Correlation analysis showed significant correlations between the DPPH and FRAP activities and the TFC. The present findings highlight that these plants are good sources of phenolic compounds and essential elements and support their therapeutic use as antioxidant drugs.