Eleven populations of pea (Pisum sativum L.) from the ICARDA Pea Germplasm Collection, comprising landraces from Mongolia, Poland, Haiti, Uganda, Spain, Eritrea, Colombia, Turkey, Denmark, Canada and Estonia, and five Portuguese commercial cultivars ('Progress', 'Television', 'Telefone', 'Maravilha' and 'Rondo') were previously assessed for lethal temperatures (LT; 2 h exposure). These ranged from 42 to 44°C, with the commercial cultivars showing the highest LT. From these populations, seven were tested for acclimation to high temperature; all showed a positive response to acclimation at 39°C (4 h exposure). To establish a correlation between LT and both morphological and agronomic characteristics, these populations were further characterized using 23 Bioversity International descriptors, throughout a randomized block design experiment, in Ponte de Lima, NW Portugal. Principal components analysis was performed on these characteristics allowing division of landraces and cultivars into four clusters. Cluster 1 included the landrace from Poland (acc. 51758) and commercial cultivars 'Progress' and 'Rondo', which are early season and dwarf type, with LT values of 43-44°C. The same LT of 'Television' (cluster 3) corresponded to a mid-early season and dwarf/intermediate type. Cluster 2, containing landrace Haiti (acc. 124634), and cluster 4 with Uganda (acc. 50223) had LT values of 42°C; both are intermediate/tall type, but Haiti is early/mid-early season, whereas Uganda is a late season type landrace. The Uganda characteristics were similar to those of Spain (acc. 123192) with the same LT of 42°C. However, Spain was not included in the cluster analysis as it was found to be an outlier through the principal components analysis. Clusters 1, 2 and 3 presented smooth peas and cluster 4 rough peas. The results show high levels of diversity among populations which may help the future use of pea germplasm collections and studies concerning temperature stress tolerance and heat shock processes.