Aneuploidy is the alteration of the normal diploid chromosome number. In the Pacific oyster, Crassostrea gigas, hypodiploid aneuploid cells have regularly been reported as has a negative correlation between this phenomenon and growth and evidence for a genetic basis. We previously demonstrated a positive relationship between a pollutant, atrazine, and aneuploidy in Crassostrea gigas adults and juveniles. To evaluate the persistence of this impact, the present study focused on a sample of the same juveniles exposed to different atrazine treatments (0.01 mg/l which represents a peak value found in a polluted environment and 0.1 mg/l) for three and a half months and evaluated them for aneuploidy after another two and a half months in non polluted conditions. Their aneuploidy level remained significantly different between the treatments applied. In addition, our study examined the offspring of the same adult population previously treated and found that these offspring exhibited significantly higher aneuploidy levels when the parents had been exposed to atrazine. These results demonstrate the persistence of the atrazine impact on Pacific oyster aneuploidy in time within and between generations and also support the genetic basis previously found for this phenomenon.