The aim of this study was to evaluate the phytotoxicity of different doses of paper pulp sludge on Alfisol soil in order to determine the potential use of the sludge as a soil improver. The organic waste was physically and chemically characterized to determine the presence of nutrients and heavy metals which is important for plant growth. The germination index (GI), the radicle length and the hypocotyl length of Lactuca sativa L. and Lolium perenne L. were evaluated for six doses of sludge/ soil: 10, 25, 50, 75, 100 and 150 t ha-1. A control without waste addition was also included. Results indicated low concentration of heavy metals in the sludge which is reflected in the non-toxic effect on seed germination. GI in Lactuca sativa L. reached a maximum in the control with 155%; however, there were no significant differences among the treatments. GI in Lolium perenne L. had the highest value at a dose of 50 t ha-1 with 143%, indicating significant differences between the treatments. The use of paper pulp sludge as a soil improver could be beneficial given the nutrient concentration, the low concentration of heavy metals and the no toxic effect depending on the species treated.