This systematic review aims to evaluate whether implantable bulking agents are superior or inferior to injectable bulking agents as second-line therapy in terms of clinical effectiveness and safety for faecal incontinence (FI). Six prospective uncontrolled trials were included. FI severity significantly improved sustainably, but not disease-related quality of life. Procedure-related adverse events hardly occurred. In nearly one quarter dislodgement of prostheses occurred. Studies were judged with moderate to high risk of bias and the strength of evidence for safety was judged to be very low. Implantable bulking agents might be a minimally invasive approach in FI treatment if conservative therapies fail.