Surface acoustic wave properties of Ba2NaNb5O15crystals are investigated in terms of electromechanical coupling coefficientk2and frequency temperature coefficients. AX‐rotated cut and aY‐rotated cut are selected for their fair coupling. Experimental verifications on a Union Carbide Ba2NaNb5O15crystal proved excellent agreement for the coupling (1.2%) and markedly better results than computed for the frequency‐temperature coefficient. The best value is measured to be as low as 1.5 ppm/K for ⟨101⟩ cut, (1¯01) propagation.