Plastic deformation by slip on (001)[100] in Ni₃Nb single crystals was investigated. The yield stress, strain rate sensitivity of the flow stress, shape of the stress-strain curve, morphology of slip markings and deformation substructures varied strongly depending on temperature. Temperature dependence of their behavior was classified into three regions. Anomalous increase in the yield stress was observed between 500 and 800°C. The anomalous strengthening is caused by dynamic strain aging, the so called Portevin-Le Chatelier effect.