Borosilicate glasses containing MoO3 and Dy2O3 were prepared by the melt quenching technique. The structure and the thermal properties of these glasses have been performed by using infrared (IR) technique at room temperature and DTA. The mechanical properties have been experimentally determined and calculated according to Makishima–Mackenzie model. The optical properties of the prepared glasses have been studied using the UV – Spectroscopy. The glass transition temperature and the optical band gap decrease with increasing the MoO3 content. The values of the optical band gap lie between 2.25–3.22 eV. The optical properties of the Dy3+ ion have been investigated using the Judd-Ofelt approach. The oscillator strengths and optical intensity parameters, Ωt = 2, 4 and 6 have been evaluated. An interesting behavior of the calculated lifetime versus total angular momentum, J, has been observed, where, the lifetime values of the 6FJ states show an exponential increase versus J.