The Spanish slug, Arion vulgaris, is considered one of the hundred most invasive species in Central Europe. The lack of natural predators can refer to the potential toxicity of slugs. However, no transcriptomic or proteomic study has been done so far in Arion vulgaris. In this study, we present the first investigation of expression profile in Arion vulgaris at the protein level. Two-dimensional (2D) gel electrophoresis and nano-LC-ESI-MS/MS were used to resolve and identify proteins from slug mantel and slug eggs. To facilitate proteomics in non-model organisms, mRNA-derived protein database was used for protein identification.