The combined effects of urban heat island (UHI), urban population growth and energy overexploitation are undermining the safety of urban areas. Urban morphology plays a prominent role in this context, because it affects building's energy demand and local climate at urban scale. However, this contribution is recurrently neglected. The present contribution seeks to investigate the direct and indirect effect of urban morphology on buildings energy performance in the Mediterranean climate. Urban morphology affects energy demand by modifying two relevant variables: outdoor air temperatures and incident radiation. The relevance of these effects were studied on a sample of urban textures of Rome and Barcelona. The study is parametric in approach. The textures were modelled and parameterized and their performances were compared. The UHI in different urban textures was calculated, by Urban Weather Generator tool. Then a sensitivity analysis of the building energy demand to the outdoor air emperatures and the incoming solar radiation was carried out, by EnergyPlus engine. Results confirm the relevance of urban morphology to the UHI intensity. Warmer temperatures lead to an average increase of energy demand from 10% to 35%, according to different urban densities. At the same time, the incident radiation reduction due to urban obstruction is desirable in Mediterranean climate; it allows a reduction of annual energy demand up to the 19% compared to an unobstructed environment. Therefore, relevant errors may occur if urban morphology’s contribution to energy demand is neglected, approximately 89% for space heating and 131% for space cooling calculations, depending on the texture density and the building orientation.