This paper reports a thermal and spectroscopic study of Pr(HCOO)3 crystal in the range 300–10 K. Room temperature Raman phonons are assigned based on group theory analysis and correlations with other rare earth formates. Differential scanning calorimetric (DSC) measurements show that there is a slight anomaly in the behavior of the heat capacity at around 140 K. Temperature-dependent Raman spectra were recorded and the changes observed are discussed. These results suggest that Pr(HCOO)3 undergoes a second-order phase transformation at temperatures lower than 140 K. Based on the group-to-subgroup relations, we propose a possible low-temperature structure and discuss the driving mechanism of the phase transformation. Copyright © 2004 John Wiley & Sons, Ltd.