Halophyte ability to withstand salt-triggered oxidative stress is governed by multiple biochemical mechanisms that facilitate retention and/or acquisition of water, protect chloroplast functioning, and maintain ion homeostasis. Most essential traits include the synthesis of osmolytes, specific proteins, and antioxidant molecules. This might explain the utilization of some halophytes as traditional medicinal and dietary plants. The present study aimed at assessing the phenolic content and antioxidant activities of some Tunisian halophytes (Cakile maritima, Limoniastrum monopetalum, Mesembryanthemum crystallinum, M. edule, Salsola kali, and Tamarix gallica), depending on biological (species, organ and developmental stage), environmental, and technical (extraction solvent) factors. The total polyphenol contents and antioxidant activities (DPPH and superoxide radicals scavenging activities, and iron chelating and reducing powers) were strongly affected by the above-cited factors. Such variability might be of great importance in terms of valorising these halophytes as a source of naturally secondary metabolites, and the methods for phenolic and antioxidant production.