Ephedra alata Decne. belongs to the Ephedraceae family. It is a species of Ephedra that grows mostly in the desert. Today, the main importance of Ephedra species in the medical field is due to the presence of the alkaloids derived from phenyl-alanine, which act on the sympathetic nervous system as a sympathomimetic. The aim of this study was to conduct a phytochemical characterization of the hydroalcoholic extract of the aerial part of Ephedra alata Decne., which is indigenous to Tunis, that involves the total phenolic content, individual phenolic content, and antioxidant activity as well as a biological screening for the evaluation of the antimicrobial, antifungal, antiproliferative, pro-apoptotic, and cytotoxic potential against the MCF-7 breast cancer cell line. The results show that the hydroalcoholic extract contains polyphenolic phytocompounds (156.226 ± 0.5 mgGAE/g extract) and elicits antioxidant activity (7453.18 ± 2.5 μmol Trolox/g extract). The extract acted as a bacteriostatic agent against all tested bacterial strains, but was bactericidal only against the Gram-positive cocci and Candida spp. In the set experimental parameters, the extract presents antiproliferative, pro-apoptotic, and cytotoxic potential against the MCF-7 human breast cancer cell line.