The possibility of formation of mixed complex compound niobium(V)-pyrocatechol (PC)-thenoyltrifluoracetone (TTA) has been shown. Optimum conditions for the formation of such a compound have been found (7.5MHCI, 0.3MTTA, 0.4MPC) and the molar ratio Nb (V):PC:TTA=1:2:2 has been established by the equilibrium shift method. The absorption spectrum of the chloroform extract of the Nb-PC-TTA compound has a maximum at 414 nm, ϵ= (7.7±0.2) × 103. The influence of other ions on extraction-photometric determination of niobium (V) with PC and TTA is discussed.