Many 2D nanomaterials have been demonstrated to possess amazing physiochemical properties and are likely to be incorporated in future consumer products. Therefore, there is a urgent need to ensure that these nanomaterials do not cause adverse health effects. In this study, the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS₂, WS₂, and WSe₂, were compared with that of graphene oxides and halogenated graphenes to determine which group of 2D nanomaterials would display better biocompatability. Cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays on human lung carcinoma epithelial cells (A549) exposed to varying concentrations of these 2D nanomaterials revealed that MoS₂ and WS₂ nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe₂ was found to exhibit dose-dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL⁻¹. In comparison with graphene oxides and halogenated graphenes, MoS₂ and WS₂ were much less hazardous, whereas WSe₂ showed similar degree of cytotoxicity, suggesting that MoS₂ and WS₂ might be suitable and safe materials for potential applications. However, future in-depth studies should be built upon this first work on the in vitro cytotoxicity of MoS₂ and WS₂ to ensure that they do not pose acute toxicity. Lastly, nanomaterial-induced interference control experiments indicated that MTT assay is not suitable for measuring the cytotoxicity of exTMDs as inflated absorbance values will be obtained due to undesired reaction between exTMDs and the MTT assay viability markers, giving false impressions that the materials are less toxic.