Peri-device leak and device-related thrombus¹ remain key challenges of current left atrial appendage occlusion (LAAO)² owing to the incompatibility between the solid occluder and the left atrial appendage (LAA). Here we propose a personalized and complete LAAO using magnetofluids that is suitable for all types of LAAs. Magnetofluids can be injected into LAAs from cardiac catheters. In the presence of a sufficient magnetic field, magnetofluids can resist high-speed blood flow. Magnetofluids can precipitate into magnetogels in contact with water in the blood within only a few minutes. We further confirmed the long-term resilience and biocompatibility of the magnetogel over 10 months in a pig model in vivo. Neither device-related thrombus nor magnetogel leakage was observed in any pigs. The endocardium formed on the Watchman occluder was rough and incomplete, predisposing to thrombosis. Myocardial injuries were unavoidable due to the barbs of the Watchman occluder. The endocardium formed on our magnetogel was smooth, firm and thrombus-free. No crevice was observed between our magnetogel and the LAA, and no injury was caused to the myocardium. These findings may offer a promising clinical strategy for long-term thrombus-free LAAO.