Haloxylon salicornicum (H. salicornicum) is a plant that is frequently taken as a tea by Bedouin women in Egypt who are experiencing difficulties during pregnancy, as well as to provide relief from dysmenorrhoea. Despite its medical use, there has been no detailed evaluation of the effect of this plant on uterine tissue. Therefore, the initial aim of this study was to determine whether H. salicornicum affected the contraction of the mouse uterus in vitro. The crude aqueous extract of H. salicornicum was found to inhibit the spontaneous contractions of the uterus, with the effect being rapid in onset and completely reversible upon washout. Subsequent purification of the plant extract resulted in the identification of synephrine and N-methyltyramine, both of which were found to have inhibitory effects on the spontaneous contractions of the uterus. The EC50 for the purified constituent identified as synephrine was 0.82 ± 0.24 μ g/mL. The inhibitory activity of crude H. salicornicum, as well as the isolated constituents, could be prevented by pretreatment of the uterus with the β -adrenoceptor antagonist propranolol. In conclusion, the use of H. salicornicum during preterm labour appears to be justified, and its pharmacologic effect is consistent with it acting as a β -adrenoceptor agonist.