Fistula in ano is a common anorectal disease in adults. Currently, surgery remains the definitive therapeutic approach, but in some cases, it can lead to serious complications as faecal or gas incontinence. Therefore, sphincter sparing treatments should be considered for complex fistulas. One of the sphincteric preserving treatment is the filling with a dermal extract commonly called “collagen glue” as Salvecoll-E® gel. This is a multicentric, prospective, observational study on the use of Salvecoll-E® gel in treatment of complex anal fistulas. We treated 70 patients from May 2016 to May 2017. In the first phase, we debrided the fistula tract using a loose seton kept for 4–6 weeks. In the second phase, the seton was removed and the fistula tract was filled with Salvecoll-E® gel. In this article, we report results at 36 months of follow-up. Fifty patients (71.4%) had completely healed fistula within 36 months of follow-up. Twenty-eight patients (28.2%) had recurrences. Among these failures, 65% were within 6 months. All low transphincteric fistulas healed. Recurrences occurred only in median and high transphincteric fistulas. No patient had a worsening of continence status measured with Cleveland Clinic Florida Incontinence Severity score. Salvecoll-E® gel is a recent finding among sphincter-sparing treatments. In this study, we demonstrate that it is a safe option in the treatment of complex fistulas. Final results are satisfactory and in line with the best results published in literature among mini-invasive treatments.