F3/2 level of Nd3+ in aluminosilicate optical fiber preforms after 807-nm excitation are reported in the temperature range from 15 °C to 500 °C for Nd2O3 concentrations in the range from 0.2 to [%wt]0.9 and Al2O3 concentrations of between [%wt]3.8 and [%wt]8. At room temperature it is observed that for concentrations of less than [%wt]0.6 Nd2O3 the fluorescence decay is approximately exponential; for the higher Nd2O3 concentrations the decay is increasingly bi-exponential. We have identified a “slow” (≈500 μs) and a “fast” (≈100 μs) decay time; the slow decay is attributed to isolated ions and the faster decay to energy transfer between homogeneously dispersed ions. The measured 1/e folding fluorescence decay time τ decreases slowly at a constant rate of -0.08±0.007 μs/K for [%wt]0.9 Nd2O3. It is shown that increasing the Al2O3 concentration tends to suppress this temperature quenching effect. A radiative decay time of 640 μs is obtained by Judd–Ofelt analysis.