Electrocatalytic conversion of carbon dioxide (CO2) has been considered as an ideal method to simultaneously solve the energy crisis and environmental issue around the world. In this work, ultrasmall Cu nanoparticle interspersed flower-like MoS2 was successfully fabricated via a facile microwave hydrothermal method. The designed optimal hierarchical Cu/MoS2 composite not only exhibited remarkably enhanced electronic conductivity and specific surface area but also possessed improved CO2 adsorption capacity, resulting in a significant increase in overall faradaic efficiency and a 7-fold augmentation of the faradaic efficiency of CH4 in comparison with bare MoS2. In addition, the Cu/MoS2 composite had superior stability with high efficiency retained for 48 h in the electrochemical process. It is anticipated that the designed Cu/MoS2 composite electrocatalyst may provide new insights for transition metal sulfides and non-noble particles applied to CO2 reduction.