A model for combined mass and heat transfer during nonisothermal absorption of a one component gas in a Vertical gas-liquid slug flow with liquid plugs containing small bubbles is suggested. Under the assumptions of a perfect mixing of the dissolved gas in liquid plugs and uniform temperature distribution in liquid plugs, recurrent relations for the dissolved gas concentration and temperature in the nth liquid plug and mass and heat fluxes from the nth unit cell of a gas-liquid slug flow are derived. The total mass and heat fluxes in a gas-liquid slug flow are determined. Theoretical results are compared with the available experimental data.