Single crystals of the noncentrosymmetric KNaNbOF5 polymorph were grown for piezoelectric and triboluminescent measurements. Piezoelectric measurements yielded a d33 value of ±6.3 pCN-1 and an effective electromechanical coupling coefficient of up to 0.1565 in the frequency range 1960-2080 kHz. Crystals of KNaNbOF5 were found to exhibit a strong triboluminscence effect visible to the naked eye as blue sparks when crystals are crushed. This triboluminescence effect is uncommon in that it is likely independent from both the piezoelectric effect and atmospheric electrical discharge. Instead, triboluminescence may originate from crystal defects or be related to an electroluminescence effect.