Low‐temperature‐processed carbon‐based perovskite solar cells (C‐PSCs) are promising photovoltaic devices, because of their good stability, low cost, and simple preparation methods, which allow for scalable processing. Herein, C‐PSCs with the n−i−p structure are prepared, using a SnO2 nanoparticles film as the electron‐selective contact, MAPbI3 perovskite as the intrinsic absorber layer (MA = methylammonium), and a carbon layer as the hole‐selective layer and conductor. Carbon is, however, not an ideal hole‐selective layer and it is found that improved solar cell performance can be obtained by introducing a polymeric hole conductor between the perovskite and the carbon layer. Specifically, undoped poly(3‐hexylthiophene) (P3HT) is used for this purpose, as it is stable and highly hydrophobic. For ITO/SnO2/MAPbI3/carbon devices, a solar cell efficiency of up to 12.8% is obtained, increasing up to 15.7% with the inclusion of a P3HT layer, which increases open‐circuit potential, photocurrent, and fill factor (FF). In comparison, ITO/SnO2/MAPbI3/P3HT/Au devices performed rather poorly (up to 11.7%). Encouraging stability is obtained for unencapsulated C‐PSC devices: P3HT/carbon devices do not show any degradation in solar cell performance upon storage for 1 month in low humidity, while they maintain 70% of their initial efficiency after 900 h at 82 °C in air.