The objective of this study was to analyze whether frozen/thawed sperm quality, in the Siberian sturgeon sperm (Acipenser baerii, Brandt, 1869), in particular if motility parameters, viability and fertilization capacity would be affected following a 4 h exposure of fresh semen to mercury and cadmium (0–100 mg L−1) prior to cryopreservation. The percentage of motile sperm was reduced at 1 mg Hg2+ L−1 and 10 mg Cd2+ L−1. The sperm's ability to fertilize was significantly lower at 10 mg Hg2+ L−1. Moreover, results showed that the negative impact of heavy metals on the sperm motility and ability to fertilize did not result from disturbances to sperm membrane integrity. The percentage of motile sperm seems to be a more useful indicator than sperm velocity for evaluating fertilization impairment in Siberian sturgeon sperm when exposed to mercury. Mercury appeared to be more detrimental than cadmium in terms of ability to fertilize. Our results suggest that the sperm of acipenserid fish may be characterized by a higher resistance to cadmium ions compared to that of the teleost fish.