A straightforward PEGylation of SWCNTs has been performed by photomediated addition of various PEG derivatives onto the nanotube surfaces. The reaction was promoted both by UV and by solar light and took place under very mild conditions using commercial PEGs as PEGylating agents. The process relies on the formation of α-oxy radicals directly from PEGs by a photochemical hydrogen abstraction reaction mediated by a decatungstate salt. Actually, low-molecular-weight PEGs (e.g. PEG 200) added more efficiently than those having long polyethylene glycol chains (e.g. PEG 600). Interestingly, the functionalization caused a partial dissolution of the resulting CNTs in the reaction medium.