Growth and morphometric characteristics of the caridean Palaemon longirostris Milne Edwards, 1837, were studied in the Gironde estuary population. Their first comparison with earlier studies in this estuary and in the Mira River provided the first step towards developing environmental indicators using a species represented at the European scale. Mean individual growth was modelled for each sex using the classical von Bertalanffy growth model and the seasonal model that integrates periods of lower growth. Morphometric relationships, in particular the spatio-temporal variability in the relative weight of individuals, were explored according to sex and physical parameters of the environment. Females grew to larger size than males. Growth estimates showed the importance of accounting for the seasonal variations to evaluate non-biased growth. Sex and the presence of eggs for females showed significant interaction within the carapace length – total length relation as well as for the carapace length – weight relation. Body condition was significantly greater in spring and summer for both sexes and was significantly correlated with salinity, but only for males. Comparison with the Mira River was limited to the range of data available. However, the population of the Gironde estuary, being similar in both recent and historical studies, showed morphometric differences when compared to that of the Mira River. Indeed, the growth performance index was higher in the Gironde estuary and likely linked to temperature constraints. Conversely, differences between males and females were much higher in the Mira River than in the Gironde estuary.