Incubation in birds takes place within a nest that is often assumed to confer a degree of thermal insulation. The range, amounts and organisation of materials used to construct nest walls hampers our understanding of the degree to which they provide insulation during incubation. This experimental study used temperature loggers in a model system to test the insulative properties of materials extracted from bird nests to determine: 1) whether differences existed in terms of insulation, and 2) if the position of a material mattered when two materials were tested in combination. Animal-derived materials offered better insulation than plant-derived materials, whether tested singly or in combination. Halving the mass of each material did not affect insulation conferred by the material proximal to the temperature logger. Differing thermal conductivities of the materials in contact with the temperature logger may explain these results. If a bird strategically places an animal-derived material only into a nest cup lining then it may be sufficient to provide good insulation for the whole nest. More research is needed to generate thermal conductivity data for commonly used nest materials to test this idea more rigorously in finite element heat transfer models.—Deeming, D.C., Griffiths, J.D. & Biddle, L.E. (2020). Material type and position determines the insulative properties of simulated nest walls. Ardeola, 67: 127-136.