We develop in this chapter how the draw resonance instability is affected by cooling through the temperature dependence of the viscosity. We first discuss the difference between isothermal and non-isothermal draw resonance in literature as well as between non-isothermal film casting and fiber drawing. Next, a non-isothermal model is derived for film casting and a linear stability analysis allows to investigate the influence of the heat transfer on draw resonance and how cooling mainly has a stabilizing effect. The prescribed temperature regime in the limit of infinite Stanton number is also identified and a scenario for the stabilizing mechanism of draw resonance due to cooling is proposed, based on phase shifts between axial tension and relevant spatially averaged quantities of the system. Finally, we test both the Jung’s and Kim’s stability criteria and show how the different times involved in those criteria are affected by cooling.