Genotoxic effects are one of the earliest signs of pollution-related environmental disturbance. In this study influence of environmental pollution was assessed by measuring DNA damage in haemocytes of caged narrow-clawed crayfish Astacus leptodactylus by the means of the comet assay and micronucleus test. Animals were collected at the reference site (the Mrežnica river) and exposed in cages for one week at the three sites of different pollution intensity along the Sava river (Zagreb, Sisak, Krapje). A separate crayfish group caged at the reference site was used as a control. On each location sediment was collected for chemical analysis. Statistically significant increase in DNA damage measured by the comet assay was observed at all three polluted sites comparing to the reference site. Micronuclei induction showed similar gradient of DNA damage, but did not reach the statistical significance. In addition, individuals from the mildly polluted site (Krapje) exposed on more polluted site Zagreb showed lower level of the DNA damage than the ones from the reference site exposed at the same location, indicating activity of adaptive mechanisms in animals from pollution stressed environment. In this survey freshwater crayfish were used for the first time as sentinel organisms in environmental genotoxicity studies. Our results have proved applicability of caging exposure of a freshwater crayfish A. leptodactylus in environmental biomonitoring and confirmed usefulness of comet assay and micronucleus test as suitable tools for detection of pollution-related genotoxicity.