Polyaryletherketones (PAEK) is a family of high performance thermoplastics that have gained interest especially in the aeronautic field because they are semi-crystalline and their aromatic chain leads to excellent chemical resistance compared to other amorphous thermoplastics. PEKK is comparable to polyetheretherketone (PEEK) in terms of mechanical performance and chemical resistance but has the particularity of having an adjustable melting temperature leading to a wider processing window. PEKK is a copolymer of both terephtaloyl isomer (T) with para phenyl links and isophtaloyl isomer (I) with meta phenyl links. The melting temperature of PEKK can be tuned by changing the T/I ratio in order to make processing of composite parts easier. During its in-service life, PEKK composite is susceptible to be exposed to different kinds of fluids, in particular water. Thus, it is essential to identify and understand water sorption kinetics as it can strongly affect mechanical properties of the composite part. The present paper aims to give a global comprehension of the water sorption kinetics in both PEKK matrix and carbon fiber reinforced PEKK composite. Gravimetric measurements are completed with Dynamic Vapor Sorption (DVS) measurements as the best method to assess both diffusion kinetics and weight gain of the materials as a function of relative humidity. DVS measurements show that fully crystallized PEKK follows Henry’s law between 0% and 90% relative humidity. In terms of diffusion process, it is shown the water absorption follows Fick’s law. The study of composite samples with controlled defect makes it possible to understand the effect of porosity on water sorption. If both consolidated and porous composites follow Henry’s law at low relative humidities, a deviation is observed at high relative humidities. A deviation from the Fickian behavior is observed for the composites as well. These deviations are investigated and discussed as a function of porosity fraction.