Social immunisation is a horizontal transfer of immunity which protects naïve hosts against infection following exposure to infected nestmates. Whilst mainly documented in eusocial insects, non-social species also share similar ecological features which favour the development of group-level immunity. Here we investigate social immunisation in Tenebrio molitor, by pairing naïve females with a pathogen-challenged conspecific for 72 h before measuring a series of immune and fitness traits. We found no evidence for social immunisation, as beetles who cohabited with a live-bacteria-challenged conspecific were not better protected against bacterial-challenge. However, exposure to a heat-killed-bacteria-challenged conspecific appeared to increase pathogen tolerance, which manifested in differential fitness investment. Our results together suggest that T. molitor do respond to immune-related cues in the social environment, despite not showing a classic immunisation response as predicted.