The bottom ash from municipal solid waste incineration is the most important by-product, in terms of energy recovery from municipal solid waste. Safe treatment and reuse of this bottom ash in construction materials is one of the ways of its effective use. The specific use precedes the study of the properties of the bottom ash from municipal solid waste incineration. In this study, samples of bottom ash were examined via sieve analysis, basic chemical parameters, ecotoxicological property analysis and determination of heavy metals (As, Cd, Cr, Cu, Pb, Ni, Zn). The sieve analyses of samples showed different contents of individual fractions. Ecotoxicological tests for acute toxicity on Daphnia magna in the raw aqueous extract showed positive results mortality of all individuals after 24 hours. The toxic effect of bottom ash was confirmed by the content of heavy metals.