The expression of oestrogen receptors (ERα and ERβ) in the prostate and uterus tissues of Wistar rats supplied for 8 weeks with a diet rich in sesame (Sesamum indicum) pericarp (30 %) was monitored. Eight male rats, aged 6 weeks, were divided into a control group fed on a normal diet, and an experimental one, provided with the normal diet enriched with 30 % sesame pericarp. A similar experiment was performed with female rats. At the end of the experiment, the prostate and uterus tissues were surgically removed and kept at − 80°C for up to 2 months. Western blotting and quantitative real-time PCR (qRT-PCR) methods were used in order to investigate the levels of receptor proteins and mRNA. Significant increase in the expression of ERβ in prostate and uterus was evident in both methods, while the magnitude of the observed alteration depended on the applied method. No statistically significant change was observed in the expression of ERα in uterus. In prostate, although the increase was more evident when investigated by means of qRT-PCR, the difference in expression of ERα was not statistically significant. In both tissues, a shift of the ratio of ERα:ERβ in favour of ERβ was evident, indicating, according to existing literature, a beneficial effect of the diet provided upon the health status of the organisms. It is suggested that this effect is attributed to the lignans present in the pericarp which exert phyto-oestrogenic activity.