Spin-polarized current through a ferromagnetic/organic interface was studied theoretically. This study was stimulated by recent experiments on La1−xSrxMnO3 /Alq3/Co and La1−xSrxMnO3/sexithienyl/La1−xSrxMnO3 structures. According to the spin-diffusion equation, the current spin polarization was obtained by assuming that spin polarons as well as spinless bipolarons to be the carriers in the organic semiconductor. It was found that polarons are the effective spin carriers of a spin-polarized current, even though they constitute only a fraction of all carriers. Effects of interfacial electrochemical-potential difference and conductivity matching on spin polarization of the current are discussed.