Layered perovskite-type K2Nd2Ti3O10 titanate is known as promising photocatalyst in the reaction of water splitting. Interactions with water lead to processes which can influence the physico-chemical properties of oxides: intercalation of water into the interlayer space and ion exchange of alkali cations to protons [1]. At the same time the composition of K2Nd2Ti3O10 can also change in a humid atmosphere that’s why the study of water sorption by K2Nd2Ti3O10 is relevant and such investigation should not be neglected. The layered perovskite-type titanate K2Nd2Ti3O10 belonging to Ruddlesden-Popper phases was synthesized by the solid-state reaction at 1100oC during 6 h in air. Protonated intercalated derivatives HxK2-xNd2Ti3O10•yH2O were obtained by continuous flushing of K2Nd2Ti3O10 by 1 and 5.5 L of water. K2Nd2Ti3O10 and HxK2-xNd2Ti3O10•yH2O were investigated in a humid atmosphere by sorption analysis (TA Instruments TGA Q5000SA) at alterable conditions of humidity. The phase composition of the investigated compounds was monitored using XRD analysis (Rigaku MiniFlex II). To determine the degree of protonation and the number of intercalated water thermogravimetric analysis (Netzsch TG 209 F1 Libra) was used. It has been found that the interaction of K2Nd2Ti3O10 with water leads to formation of two stable phases: H1.64К0.36Nd2Ti3O10·0,61 H2O (phase I) and H1.89К0.11Nd2Ti3O10·0,60 H2O (phase II). While the initial layered oxide crystallizes in a tetragonal I4/mmm space group and its hydrated form - in a P4/mmm s.g., it was found that the crystal symmetry loweres upon protonation during water flushing to C222 s.g. Sorption analysis of Phase I and Phase II at 0 ̶ 95 ̶ 0% RH demonstrated that they are resistant to further intercalation and protonation processes. Water sorption ̶ desorption processes are observed for these compounds only. Concerning K2Nd2Ti3O10, sorption analysis presented that the sorption-desorption isotherm is not-reversible and characterized by mass change as a result of intercalation and protonation processes. Scientific research was performed at Center for Thermogravimetric and Calorimetric Research and Center for X-ray Diffraction Methods of St.Petersburg State University.