We demonstrate a liquid-crystal (LC)-tuned Tamm-plasmon (TP) resonance device. The term TP polariton refers to plasmonic resonance at the interface between a photonic crystal (PC) and a metallic film. We formulate a precise optical analysis of the proposed device using the transfer-matrix method. A single resonance dip in the photonic band-gap region guarantees that the thickness of the LC layer between the PC and the metallic film can be as small as about 180 nm. Tuning phase retardation in the LC layer is shown to shift the resonance wavelength tens of nanometers, depending on the birefringence and width of the LC layer. Simulation results are in good agreement with the experimental data.