The annual consumption of “yerba mate” (mate herb infusion) in Uruguay generates about 125 metric tons of organic waste. Vermicomposting is one way to obtain organic matter by recycling organic household waste. The waste of “yerba mate” has a great potential for recycling if it is used as a substrate in vermicomposting. Using different substrates, composting times and volumes of “yerba mate” we determined some of the necessary conditions for the use of yerba mate waste as a substrate for the Eisenia fetida earthworm. We studied the optimal pH conditions that the waste should have in order to be tolerated and best exploited by the worms and the period of time that the “yerba mate” takes to achieve these conditions. We observed that four weeks is the minimum amount of precomposting time of “yerba mate”, recquired by the worms for an improved processing of it. The vermicompost obtained was analyzed. The following analysis were performed: organic matter, Nitrogen, Phosphorous and metals. The values found for Nitrogen (1 %) and organic matter (which was around 30 %) are parallel to the values found for other composts which are obtained by similar composting methods. However, the value of Phosphorus was found to be lower than that found in the analysis performed by CUI (Ambiental Laboratory Echotech, October 2006).