Purpose Colostomy is a frequent event in oncological or inflammatory bowel diseases. Its related morbidity includes retraction, infection and parastomal hernia (PH), which is a quite common late complication. Several surgical options are available for PH repair, the majority including mesh. However, results are often disappointing with relevant recurrence rates, up to 33%. The study aim was to assess the feasibility and effectiveness of prophylactic biosynthetic mesh (BIO-A ® , polyglycolide-trimethylene carbonate copolymer) placed during colostomy fashioning, in reducing PH. A prospective randomized controlled double-blind trial was conducted from January 2014 to December 2019 to compare conventional end-colostomy with end-colostomy reinforced with BIO-A mesh in ante-rectus position in patients undergoing colon diversion in emergency surgery. Methods Patients were clinically followed up at 3, 6, and 12 months and received a CT scan at 6 and 12 months. The postoperative morbidity and wound events were also evaluated. Results 55 patients receiving conventional colostomy considered as Control Group and 55 patients receiving BIO-A mesh supported colostomy (Mesh Group) were included in the study. At 12 months, the incidence of PH was 9 (12.7%) and 24 (43.6%) in the Mesh Group and Control Group, respectively ( p  < 0.05). Postoperative morbidity was similar between Mesh Group and Control Group (7 12.7% vs 4 7.3%, respectively; p  = 0.340). The multivariable analysis showed that not using a mesh ( p  = 0.042), age > 70 years ( p  = 0.041), diabetes ( p  < 0.001), colon dilation > 7 cm ( p  < 0.0001) and COPD ( p  = 0.009) were all related with postoperative PH. Conclusions The prophylactic BIO-A mesh positioning during colostomy is an effective procedure reducing PH incidence at a 1 years follow-up guaranteeing low postoperative morbidity. Study dataset is available on ClinicalTrials.gov ID NCT04436887.