Transparent CaO-Al₂O₃-B₂O₃ glasses codoped with Tm³+ and Er³+ were prepared by melt quenching and subsequent heating. Optical absorption spectra revealed an ultraviolet to visible absorption band corresponding to a relative electronic transition of Tm3+ and Er³+. For Tm-only doped glasses, the 791-nm absorption line is prominent and also has comparable strength in Tm-Er codoped glasses. Both 405-nm and 791-nm wavelengths have been used as excitation sources to comparatively study the photoluminescence characteristics of Tm3+ and Er3+. Only Er3+ emission at 1528 nm has been observed under a pumping wavelength of 405 nm. However, both Tm3+ and Er³+ emission can be found with an excitation wavelength of 791 nm. It implies that 791 nm should be very effective for pumping Tm-Er codoped aluminate glass for application in broadband optical waveguide amplifiers.