<p><i>Campomanesia adamantium</i> (Cambess.) O. Berg is a native Brazilian species with promising compositional and functional attributes. Its leaves contain a variety of phenolic compounds and volatile constituents with potential antioxidant properties, but their food applications remain poorly explored. This study evaluated the influence of leaf particle size on the physicochemical composition, bioactive profile, and sensory properties of <i>C. adamantium</i> infusions, with commercial teabag applications in mind. Leaf samples were ground to three granulometries (10, 20, and 32 mesh) and infused using distilled or tap water to simulate controlled and domestic preparation conditions. Physicochemical parameters, total phenolic, flavonoid, and tannin contents, antioxidant potential, and liquid chromatographic analysis were performed. A consumer panel (<i>n</i> = 100) assessed appearance, aroma, taste, astringency, flavor intensity, and purchase intention. Finer particles increased the extraction efficiency, resulting in higher antioxidant activity, particularly in infusions prepared with distilled water. However, sensory acceptance decreased for the 32-mesh samples. The 20-mesh particle size provided the optimal balance between chemical composition and sensory acceptance. These results demonstrate the potential of <i>C. adamantium</i> leaves for the development of value-added infusions, underscoring the influence of water composition on extractability.</p>