ZnWO4 with controllable morphology was successfully synthesized via a facile hydrothermal method. The relationships between the structure, morphology, and catalytic activity were systemically studied by varying both the hydrothermal time and pH value. The optimal synthesis conditions for ZnWO4 with superior catalytic activity were a hydrothermal time of 12 h and a pH value of 10. Impressively, the highest photocatalytic activity for the degradation of RhB was 91% for 60 min under ultraviolet light. The increased photodegradation performance was mainly ascribed to the high crystallinity and enlarged surface area of the optimal ZnWO4.