Spectroscopic properties of praseodymium ions-doped erbium oxalate ($Er_2(C_2O_4)_3 \cdot nH_2O$) crystals have been investigated. The crystals were grown by hydro silica gel method under suitable pH conditions and by single diffusion method. The well-grown crystals are bright and transparent. The dark green colour of these crystals changes with the variation of the concentrations of the dopant ions. The absorption spectra have been measured in the region 200–800 nm at room temperature. Judd–Ofelt intensity parameters for f–f transitions of the $Pr^{3+}$ ions have been determined as $\Omega_2 = 166.7$, $\Omega_4 = 1.103$ and $\Omega_6 = 2.898$. Analyses of the absorption spectra also show a possible energy transfer from the host material to the dopant.