We report the recent arrival and subsequent spread of the Sida Leafbeetle, Calligrapha pantherina Stål, 1859, in the archipelago of New Caledonia. The species seems to have a rapid spread as it is now recorded all along the west coast and also have spread to the Loyalty Islands. The first specimen was caught in November 2012. This is a biocontrol agent which was introduced in the Pacific Region against invasive Malvaceae (Sida spp.). This accidental arrival would help to control the alien weed, Sida acuta Burm. f., in New Caledonia. But this establishment raises some questions about potential threats on the two endemic New Caledonian Sida species. We also discuss this arrival and subsequent installation in the context of global change and biosecurity issues, particularly in such a biodiversity hotspot.