Abstract Different thicknesses of amorphous silicon carbide (a-SiC) and amorphous silicon nitride (a-Si x N y ) coatings were deposited on randomly aligned multiwall carbon nanotubes (MWNTs) by plasma enhanced chemical vapor deposition (PECVD). Their optical limiting properties were studied as a suspension in water. Optical limiting experiments show that they had slightly reduced optical limiting properties compared to pure MWNTs, the extent depending on the thickness and coating material. However, the linear transmission spectra of these coated MWNTs show a broader band transmission than pure MWNTs. This suggests that the coated MWNTs are more ideal as protective material for optical sensors as compared to pure MWNTs because they are effective over a wider optical transmission band.