High-performance flexible batteries are promising energy storage devices for portable and wearable electronics. The major obstacle to develop flexible batteries is the shortage of flexible electrodes with excellent electrochemical performance. Another challenge is the limited progress in the flexible batteries beyond Li-ion because of safety concerns for the Li-based electrochemical system. Accordingly, a self-supported tin sulfide (SnS) porous film (PF) was fabricated as a flexible cathode material in Al-ion battery, which delivers a high specific capacity of 406 mAh/g. A capacity decay rate of 0.03% per cycle was achieved, indicating a good stability. The self-supported and flexible SnS film also shows an outstanding electrochemical performance and stability during dynamic and static bending tests. Microscopic images demonstrated that the porous structure of SnS is beneficial for minimizing the volume expansion during charge/discharge. This leads to an improved structural stability and superior long-term cyclability.