The efficiency of perovskite/Cu(In,Ga)Se2 (CIGS) tandem solar cells has been limited by interfacial challenges. Now, a dual-interface engineering strategy enables conformal perovskite coverage on textured CIGS bottom-cell surfaces while increasing carrier extraction at the electron‑ and hole‑transport interfaces. This strategy enables monolithic perovskite/CIGS tandems with a power conversion efficiency of >30% and good stability.