Oomycetes are significant pathogens responsible for causing various plant and animal diseases, including root rot, potato blight, and kauri dieback, which can lead to substantial biodiversity and economic losses. Their infection strategy includes the production of asexual zoospores, which can play a crucial role in their spread to neighbouring plants and animals. Recent research has highlighted turgor regulation, the ability to control internal hydrostatic pressure, in asexual encysted zoospores of the oomycete Achlya bisexualis. This mechanism potentially enables spores to withstand environmental stresses, thereby increasing their longevity and infectivity. The objective of this study is to investigate whether turgor regulation is also present in the encysted and swimming zoospores, and hyphae of another more destructive oomycete, Phytophthora nicotianae, which affects agricultural plants globally. The encysted zoospores, swimming zoospores and hyphae were osmotically shocked with sorbitol, sucrose and sodium chloride at varying concentrations ranging from 0.1 – 0.7 M and morphological changes were investigated using differential interference contrast (DIC) microscopy. Plasmolysis in encysted zoospores was observed post osmotic shock in osmoticum solutions of concentrations > 0.3 M. After initial plasmolysis the protoplast deplasmolysed, indicative of a recovery of turgor. The rate of de-plasmolysis was dependent on the solute concentration used to impart the osmotic shock, with higher concentrations taking longer. In most cases the protoplast volume had returned to that prior to the shock within 60 minutes. After turgor recovery the encysted zoospores were viable with more than 82.5% germinating to form germ tubes. Swimming zoospores, which do not contain a cell wall were able to resist hypo-osmotic shock, likely due to their water expulsion vacuoles. However, swimming zoospores burst upon hyper-osmotic shock, suggesting that there is no mechanism in the wall-less spores to decrease cellular osmotic potential, either through mechanisms involving metabolism or membrane transport. This suggests a key difference in the physiology of swimming wall-less spores and encysted spores. No plasmolysis of P. nicotianae hyphae was observed in hyphae after an osmotic shock, but rounding and widening of the hyphal tip was present. Forty-five minutes after osmotically shocking the hyphae they had returned to their normal morphology at the tips. A better understanding of turgor regulation in Phytophthora zoospores means that we may be better able to address their longevity and infectivity, potentially improving disease management, agricultural yields, and the conservation of native species.