It is widely accepted that secondary organic aerosols formed from the atmospheric processing of biogenic and anthropogenic VOCs represent a major component of particulate matter globally, affecting air quality, meteorology and climate, but predictive skill in atmospheric models remains poor. It has previously been theorised that water vapour may assist organic molecules forming particulates by condensing together, but until now this process has not generally been implemented in models. This paper demonstrates that by including this process using a new efficient parameterisation in the popular GEOS-CHEM global chemistry model, the effects on predicted aerosol formation can be substantial, so this effect warrants consideration going forward.