Flexible sigmoidoscopy has emerged as a vital tool for the purpose of assessing colorectal anastomoses: a procedure that can play a crucial role in reducing postoperative complications. The present technical note aims at describing a comprehensive strategy for the perioperative evaluation of colorectal anastomoses integrity. An endoscopic grading system is utilized to categorize findings, ensuring consistency and external validity. Postoperative flexible sigmoidoscopy can evaluate anastomotic integrity using a classification system, thereby facilitating informed decision-making and enabling targeted local treatment options. Additionally, flexible sigmoidoscopy can be carried out post-discharge from the hospital for further assessment of late-onset anastomotic leakage. While a consensus on the utility of flexible sigmoidoscopy is yet to be established, its potential to improve surgical decision-making is evident.