This work was carried out to assess the effects of chronic mild stress (CMS) on thyroid function. The CMS model produced an anhedonic effect (reduced preference to sucrose) in Sprague-Dawley and Wistar rats and this effect was reversed by imipramine (IMI) treatment. The effects of CMS on thyroid function were assessed by measuring tT4 (total Thyroxine), tT3 (total Triiodothyronine), TSH (Thyroid Stimulating Hormone) and fT4 (free Thyroxine) serum levels with appropriate immunoassays. CMS increased tT4 and tT3 serum levels in Sprague-Dawley and Wistar rats, but not TSH and fT4 serum levels. Imipramine (IMI) treatment normalized tT4 values. Albumin which binds a fraction of peripheral tT4 and tT3 was also significantly increased in response to CMS, possibly contributing to tT4 and tT3 elevations. The above findings suggest an impact of CMS on thyroid function, especially in tT4 values the changes being reversed with IMI treatment.