(1) Background: this study describes bioactive compounds in the following halophytes: Sarcocornia (S. alpini, S. pruinosa, and S. perennis) and Arthrocnemum (A. macrostachyum). The material comes from: coastal marshes in Tinto River, Guadiana River, and some interior provinces from the Iberian Peninsula. (2) Methods: the techniques used were Folin–Ciocalteu, GC-MS, and ESI-MS/MS. (3) Results: Five phenolic acids were found in Sarcocornia: trans-cinnamic, salicylic, veratric, coumaric, and caffeic acids. In addition, in Arthronemum, ferulic acid was also detected. The obtained flavonoids were cyanidin-3-O-arabinoside, luteolin-7-glucoside, dihydroquercetin, and p-coumaroyl-glucoside. They also presented fatty acids, such as palmitic, linoleic, and oleic acids in Sarcocornia, while palmitic, linolenic, and stearic acids were the main fatty acids in A. macrostachyum. (4) Conclusions: the high diversity of the compounds identified confirms the relation between nutritional interest and salt tolerance in halophytes.