The present study evaluates the concept of permeable reactive barrier (PRB) coupled with microwaves (MWs) as in situ-regenerating technology with focus on Cs-contaminated water. Experimental and modelling results data from batch and column tests were carried out, evaluating several chemical-physical and environmental parameters. Main results showed a very rapid increase in GAC temperature during MW irradiation up to ∼680 °C. This highlights the GAC strong ability to transform MW power into heat due to GAC excellent dielectric properties (ε′ = 13.8). Physical characterization revealed that GAC pore volume and specific surface area change with the number of regeneration cycles. GAC regeneration efficiency variation reflects this behaviour with a maximum value of ∼112% (5th cycle). The final GAC weight loss of ∼7% further demonstrates GAC life span preservation during MW irradiation. Results from column tests confirms that GAC can be regenerated by MW also in dynamic condition, due to sublimation/vaporization and vapour stripping Cs removal mechanisms and that the regeneration effectiveness is time-dependent. The breakthrough curve shape confirms significant benefits from MW irradiation. Overall, obtained finding demonstrated the feasibility of the proposed concept, also providing essential data to guide its scaling-up application. Display omitted •A new pedrmeable reactive barrier system coupled with microwaves (MW-PRB) is shown.•MW-PRB feasibility is assessed on Cs-contaminated groundwater in laboratory tests.•Activated carbon dielectric properties enhance the efficiency of MW regeneration.•Results revealed the preservation of activated carbon life span during MW irradiation.