Two commonly consumed spices in Nigeria—Piper nigrum (leaf and seed) and Monodora myristica (seed) were evaluated for natural antioxidant potentials in complementary in vitro assay systems. Extracts of the tested plant parts contained low amounts of antioxidant compounds: 4.00 - 6.65 μg GAE/mg and 2.50 - 10.38 μg RE/mg for phenols and flavonoids respectively. The extracts scavenged DPPH and hydroxyl radicals in the range of 4.32% - 37.37% (inferior to ascorbic acid and gallic acid used as standards) and 6.43% - 17.10% respectively. In the reducing power and phosphomolybdenum assays, the extracts showed ability to reduce Fe (III) and Mo (VI) ions to their lower valence states of Fe (II) and Mo (V) respectively, although these activities were inferior to those of the standards used. Comparatively, Monodora myristica seed extract was superior to Piper nigrum leaf and seed extracts in antioxidant potential, but all the extracts generally showed dose-dependent antioxidant activities. Evidently, the studied spice plants are not without some natural antioxidant capacity and would contribute appreciably in combating free radical damages when consumed.