Chalcogenide glasses are renowned inorganic materials with remarkable applications in the field of optoelectronics. In this work concentration dependent thermal diffusivity of Ge25Se65Sb10 and Ge25Se60Sb10Ag5 chalcogenide glass nanocolloids have been analysed using dual beam thermal lens technique. Nanocolloids of five different concentrations from each composition were prepared by dissolving finely powdered bulk glasses in organic solvent ethylenediamine (EDA). Enhancement in thermal diffusivity observed with increase in solute concentration is attributed to increased number of localised defects states, phonon scattering at particle liquid interface and Brownian motion of the particles. Chalcogenide nanocolloids also exhibit improved thermal diffusivity on incorporating silver to the glass matrix by replacing selenium. Results are discussed on the basis of factors such as increased nanoparticle surface area, microconvection, nanoparticle clustering, increased network connectivity and rigidity etc. •Thermal diffusivity (TD), an important thermo-optic effect characterises heat transfer ability of materials.•Dual beam thermal lens technique has been used to analyse TD in solution processed GeSeSb and GeSeSbAg chalcogenide glasses.•TD increases with solute concentration which further enhances with the addition of more metallic element silver in glass matrix.•Results reveal the possibility of tuning optical band gap, photoluminescence and thermal diffusivity in solution processed chalcogenide glasses.