AbstractA gelation solvent containing a diamide‐based thixotropic additive with two hydrocarbons and organo‐modified nanodiamonds was prepared and evaluated herein as a coating film. Nanodiamonds were introduced into a solvent containing diamide‐based thixotropic additive molecules with 12‐hydroxystearyl chains which were uniformly dispersed due to organic chain modification on the outermost layer surface. In addition to common solvents including toluene, ethyl cetyl hexanoate, a cosmetic emollient, forms nanodiamond‐containing gels. The helical nanofibers formed by the diamide‐based thixotropic additive molecule with two hydrocarbons in the gel showed affinity for the organo‐modified nanodiamonds, and the contact morphology between the nanofibers and nanodiamond particles was confirmed. Nanodiamonds exhibited a denaturation effect on biomolecules adsorbed on their surfaces. Overall, nanodiamond‐containing emollient gels are expected to exhibit antibacterial properties against viruses and malodorous bacteria on skin as part of thixotropic immobilization films for cosmetic powders.