This study represents a comparative analysis of secondary metabolites content, antioxidant, and antimicrobial activity of 24 halophytes from coastal saline habitats of the Balkan Peninsula (Montenegro, Albania, and Greece). Total content of phenolics, flavonoids, tannins, anthocyanins, antioxidant, and antimicrobial activity was determined for dry methanolic (DME) and crude water extracts (CWE) and compared with well-known medicinal plants. The total phenolic content ranged from 13.23 to 376.08 mg of GA/g of DME, and from 33.68 to 511.10 mg/mL of CWE. The content of flavonoids ranged from 12.63 to 77.36 mg of RU/g of DME, and from 12.13 to 26.35 mg/mL of CWE. Total tannins and anthocyanins varied from 0.05 to 2.44 mg/mL, and from 1.31 to 39.81 µg/L, respectively. The antioxidant activity ranged from 1147.68 to 15.02 µg/mL for DME and from 1613.05 to 21.96 µg/mL for CWE. The best antioxidant properties, and the highest content of phenolic compounds, were determined forPolygonum maritimumandLimonium vulgarewith values similar to or higher compared to the medicinal plants. Halophytes with significant antimicrobial potential wereLimonium vulgare,L. angustifolium, andArtemisia maritima. Some of the analyzed coastal halophytes can be considered rich natural sources of phenolic compounds, with favorable antioxidative and antimicrobial properties.