It is well known that oceanic internal waves (IWs) can be generated by several mechanisms, among which is tidal flow over shallow bathymetry and atmospheric forcing. In recent years, theoreticians have hypothesized that IWS generation can take place also without external forcing involved. This requires unbalanced flow as encountered in the sub-mesoscale regime of the ocean. Thus, sub-mesoscale eddies (SMEs) came into the focus of theoreticians as a source of IWs, but no observational evidence has been presented until now. In this paper, we present, for the first time, observational data that show that ISWs can be generated by SMEs. To this end, we have analyzed 5 high-resolution synthetic aperture radar (SAR) images acquired by the Sentinel-1 satellite in the Adventure Bank area of the Strait of Sicily in the Mediterranean Sea, which show sea surface signatures of ISWs surrounding SMEs. To support our interpretation of the SAR images, we have used as ancillary data high-resolution sea surface temperature (SST) and chlorophyll-a (Chl-a) data from the SLSTR and the OLCI sensors onboard the Sentinel-3 satellites, as well as model hydrology and currents. The ISWs radiate from SMEs formed during the decaying stage of cold filaments, which have their origin in upwelling events along the southern coast of Sicily.