Aim The purpose of this trial was to compare the effectiveness of sacral neuromodulation (SNM) with a submucosal injection of collagen (Permacol (R)) in women with faecal incontinence following obstetric anal sphincter injury (OASIS). Method This single-blinded randomized controlled trial at two hospital units in Norway included women with faecal incontinence following OASIS. Eligible women who had had a successful percutaneous nerve evaluation were randomly assigned to SNM or Permacol (R). The primary outcome was the difference in the St Mark's incontinence score between baseline and 6 months. Secondary outcomes were changes in the disease-specific quality of life (FIQL) and urinary incontinence (ICIQ-UI-SF) scores. Results Fifty-eight women were randomly assigned to SNM (n = 30) and Permacol (R) (n = 28). The reduction in the St Mark's score between baseline and 6 months was 11.2 (SD 5.3) in the SNM group vs 2.3 (SD 5.0) in the Permacol (R) group, resulting in a difference of 8.9 (95% CI: 6.1-11.7, P < 0.0001). The differences in the four scales of FIQL (lifestyle, coping, depression, embarrassment) were 0.90 (95% CI: 0.50-1.30, P < 0.001), 1.05 (0.62-1.47, P < 0.001), 0.52 (95% CI: 0.16-0.87, P = 0.005) and 0.95 (95% CI: 0.50-1.40, P < 0.001), respectively, in favour of SNM. The difference in the ICIQ-UI-SF was 5.0 (95% CI: 1.97-8.02, P = 0.002) in favour of SNM. There were nine minor adverse events in the SNM group compared with seven in the Permacol (R) group (P = 0.77). Conclusion SNM was superior to Permacol (R) in terms of reduction of St Mark's score, ICIQ-UI-SF and the change of the FIQL in women with faecal incontinence following OASIS.