Transition metal dichalcogenides (TMDCs) have emerged as highly intriguing materials due to their unique tunable band gap properties with layer number, finding applications in optoelectronic devices. TMDCs have been considered as potential hydrogen evolution reaction (HER) catalysts. Here we describe the hydrothermal synthesis of WS2, a promising TMDC material for efficient HER, under various conditions, and its structural, optical and magnetic and electrochemical studies are discussed in detail. The WS2 nanoflakes have good optical absorption property in region of 400–700 nm and the photoluminescence spectra show the excitation-dependent emission from two peaks corresponding to A and B excitons due to the polydispersity of nanoflakes. WS2 nanoflakes show room temperature ferromagnetism, which is attributed to the presence of zigzag edges in the magnetic ground state at the grain boundaries. The electrochemical results make them a potential candidate in energy conversion. The tunable optical and magnetic properties of WS2 could empower a great deal of flexibility in designing atomically thin optoelectronic and spintronic devices. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to The Materials Research Society.