The novel antidepressant agomelatine is an agonist of melatonin receptors (MT1 and MT2). This drug has also serotonin 2c receptor antagonist properties. There is no evidence with regards to agomelatine action on smooth muscle contractility. Aim of this study was to investigate effect of agomelatine on spontaneous and prostoglandin F2 alpha (PGF2 alpha) induced myometrial contractions in rat. Myometrial strips from adult Wistar rats suspended in a jacked tissue bath and isometric contractions were measured. Spontaneous control contractions were recorded for 10 min and increasing concentrations of agomelatine were added cumulatively. The amplitude and frequencies of contractions were evaluated by 10-min intervals before and after agomelatine doses and data are presented as mean±SEM. Same protocol was applied on PGF2 alpha induced contractions. Calcium free condition was set , and contractions were disappeared immediately because of lack of extracellular calcium source in the other protocol. This silent period (no contraction) was recorded for 10 mins and PGF2 alpha was added to the organ bath after agomelatine pretreatment. Friedman’s Two-Way Analysis of Variance was used for statistical analysis. The mean peak amplitudes of contractions were 2.64±0.2, 2.41±0.2, 2.12±0.2, 1.14±0.3 g and mean frequency of contractions were 9.37±0.5, 8.50±0.5, 7.25±1.1, 5.00±1.6 and 3.25±1.5 under control conditions and after application of 5ug/ml, 10ug/ml, 25ug/ml and 50ug/ml agomelatine in spontaneous contraction protocols, respectively. Peak amplitude was significantly decreased after application of 25ug/ml and 50ug/ml agomelatin compared to control (p<0.05 and p<0.001, respectively). Significant decrease in frequency was achieved only after application of 50 ug/ml agomelatine (p<0.01). Agomelatine completely abolished the spontaneous contractions at 125ug/ml dose. In PGF2 alpha induced protocols, mean peak amplitudes of contractions were 3.07±0.23, 2.99±0.23, 2.69±0.18 and 1.04±0.39 gram and mean frequency of contractions were 13.71±0.6, 13.29±0.6, 13.00±0.7 and 6.43±2.3 under control conditions and after application of 5ug/ml, 10ug/ml and 25ug/ml agomelatine, respectively. Agomelatine significantly decreased peak amplitude at 25ug/ml concentration (p<0.01) and completely abolished the contractions at 50ug/ml concentration. In calcium free medium, following 7 minutes pre-treatment with agomelatine (100ug/ml) completely prevented response to PGF2 alpha. Data from current study revealed for the first time that agomelatine has inhibitory effect on spontaneous and PGF2 alpha induced myometrial contractions in a dose dependently manner in rat. Mechanism(s) of inhibitory action of agomelatine on myometrial contractility may involve inhibitory actions on intracellular calcium signalling.