In this study, the physical and chemical properties of untreated, lime-stabilized and composted wastewater sludges from a Finnish pulp, board and paper mill integrate were compared in order to assess their fertilizer properties based on the requirement of the Finnish Fertilizer Product Decree. Furthermore, the extraction properties of heavy metals in sludges were assessed by the three-stage sequential extraction procedure of the Community Bureau of Reference (BCR) and the solubility indexes for heavy metals were calculated in order to evaluate the release potential of elements from the sample (sludge) matrix. The results of this study indicated that the total heavy metal (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) concentrations in all sludges were lower than the statutory Finnish limit values for fertilizer products. However, the untreated sludge required either lime-stabilization or composting in order to fulfil the Finnish maximum concentrations of pathogens (coliforms and Escherichia coli) for fertilizer products.