Er-doped MoO3 materials were prepared by a facile method. The X-ray diffraction and Raman results show that the MoO3 phase belongs to the orthorhombic phase and the Er ions have been successfully doped into the lattice space of MoO3. The near band edge emission and defect-related emissions from MoO3 and the intense sharp characteristic emission lines corresponding to Er3+ intra-4f shell transitions are resolved in the photoluminescence spectra at room temperature. The existence of the shoulder peaks due to the Stark splitting effects indicates the low symmetry of crystal field around Er3+ ions. An energy transfer mechanism from MoO3 host to Er3+ ions is proposed.