Schistosomiasis is a public health problem in many developing countries. Control of the snail intermediate hosts of Schistosoma is a promising method for eliminating this disease. Copper (Cu-chl) and magnesium chlorophyllin (Mg-chl) are potent photosensitisers used in diverse biological applications. Their effects on the fecundity of Biomphalaria alexandrina (Ehrenberg): its reproductive rate (R0) and total levels of progesterone, testosterone and estradiol were evaluated. Besides, we determined the production of cercariae of S. mansoni. The concentrations LC10 and LC25 of Cu-chl and Mg-chl significantly reduced the fecundity and R0 of the treated snails which could be partially due to the decrease in the level of steroid sex hormones. The reduction rates of R0 for the snails treated with LC10 Cu-chl and Mg-chl were 72.7% and 89.7%, respectively. Moreover, Cu-chl and Mg-chl significantly suppressed the cercarial production which dropped from 9,778 cercariae per snail in the light control group to 3,126 and 107 cercariae per snail in the groups treated with LC10 Cu-chl and Mg-chl 21 days after exposure to miracidia, respectively. Since Cu-chl and Mg-chl negatively interfere with the parasite transmission, they should be considered in schistosomiasis control programmes.