Concrete exposed to cyclic wetting and drying in salty water conditions is thought to be subjected to an accelerated ingress of chloride from the outside environment, and prone to a worsening deterioration process inside. Additionally, there is an osmotic effect on salty water flow in porous concrete. However, so far, a fully profound understanding of the coupled cyclic wetting–drying and osmosis effects on the chloride movement in concrete is still limited. This paper reports on a comprehensive study on the topic. A series of experimental tests was conducted initially for the vapour-water sorption isotherm (VWSI) of normal concrete of different porosity and chloride content. Thereafter, a novel mathematical model was proposed and validated to characterise the effect of chloride salt on the vapour absorption and water retention behaviour of concrete. Finally, the proposed characteristic model was implemented in a numerical model to simulate chloride ingress in concrete in tidal zones. The vapour-water sorption isotherm model successfully provides an effective tool to quantify the coupled influence of cyclic wetting–drying and osmosis on chloride transportation in concrete.