To date, growing interest has been devoted to fabricating graphene–metal oxide hybrid composites for a plethora of applications including photocatalysis. However, controllable synthesis of such composite materials by virtue of facile and rational routes still remains challenging. Herein, we report, for the first time, the design of an in situ, ultrasonic-assisted growth strategy for the tailored production of well-dispersed, rhombus-shaped ZnMoO_x/reduced graphene oxide (RGO) composites. The resultant composites exhibit a superior and recyclable natural-sunlight-driven photocatalytic activity toward the degradation of Rhodamine B, where the highest photocatalytic degradation efficiency can be achieved for the ZnMoO_x/RGO composites with 3 wt% RGO dosage. In addition, the synthesized hybrids possess a high areal capacitance with a good cycling performance, as well as an interesting noticeable antibacterial activity, offering special insights into the usage of such composites for a wide range of applications.