A facile process is developed to synthesize MoS₂ in basic solutions via a hydrothermal route by employing ammonium heptamolybdate and thiourea as starting materials and post-annealing in a N₂ atmosphere at 450 °C for 5 h. The morphologies of the MoS₂ products can be tuned from porous flowers to dense spheres by addition of NaOH. Experimental results show that the MoS₂ products have good crystallinity. A formation mechanism of the MoS₂ is proposed in which the dense MoS₂ spheres are evolved from the porous MoS₂ flowers through growth along the 〈00l〉 direction of the nanosheets. Based on the growth mechanism, the microstructure of MoS₂ can be successfully controlled by adjustment of the S/Mo ratio or addition of a surfactant in the recipe. Electrochemical measurements demonstrate that the flower-like MoS₂ shows better electrochemical performance than MoS₂ spheres as anode materials for Li-ion batteries, which deliver a high reversible capacity of 900 mA h g⁻¹ at a current density of 100 mA g⁻¹, excellent cycling stability and rate capability.