Abstract <p>A pyridine-calix[4]arene hydroxamic acid ligand, 5,17-dinitro-25,26,27,28-tetrahydroxy-11,23-calix[4]arene-<i>bis</i>[pyridyl hydroxamic acid] (PC4AHA), was evaluated as an analytical reagent for the extraction, preconcentration, sequential separation, and trace determination of niobium(V) and tantalum(V) from hydrochloric acid media. The method was optimized with respect to HCl concentration, ligand concentration, solvent, phase-volume ratio, shaking time, and matrix-ion tolerance. Niobium(V) was quantitatively extracted from 10 M HCl into <i>n</i>-octanol, whereas tantalum(V) was quantitatively extracted from 8 M HCl into dichloromethane. The Nb(V)-PC4AHA and Ta(V)-PC4AHA complexes showed maximum absorbance at 352 and 390 nm, with molar absorptivities of 1.90 × 10⁵ and 8.74 × 10⁵ L mol^–1 cm^–1, respectively. The spectrophotometric limits of detection were 0.099 and 0.033 μg mL^–1 for Nb(V) and Ta(V), and the corresponding limits of quantification were 0.30 and 0.10 μg mL^–1. Direct ICP-MS measurement of the organic extracts provided ng mL^–1-level confirmation. Sequential extraction enabled the determination of Nb(V) and Ta(V) in mixed solutions and in reference materials with recoveries close to 100%. The work supports the use of PC4AHA as a selective analytical ligand for trace Nb and Ta determination, while applications to rare-earth- or actinide-rich matrices require additional validation.</p>