The objective of this work is to develop a vermicomposting system that can process twophase olive mill waste. The earthworm chosen for the vermicomposting system is Eisenia fetida. To avoid toxicity problems due to the high concentration of polyphenols in olive mill waste (OMW), mixtures of OMW with cattle raw manure (CRM) and wheat straw (WS) were tested. The two mixtures, OMW+CRM and OMW+CRM+WS were put in vermicomposting reactors and compared to a vermicomposting reactor containing cattle raw manure only as a positive control.