Objective To review the application of mini-midline catheters (MMCs) in adult patients with difficult venous access (DVA), and to provide evidence for clinical practice. Methods A scoping review was conducted following the PRISMA-ScR framework. Chinese and English databases were systematically searched from inception to January 10, 2025, and literature meeting the criteria was included. The catheter insertion success rate, dwell time, complications, and health economic indicators of MMCs were comprehensively analyzed. Results Eighteen articles were included. The first-attempt success rate of MMCs insertion in adult patients with DVA ranged from 61% to 100%, with an overall success rate of 90% to 100%. The average dwell time was 4.04 to 15.40 days, superior to the peripheral venous catheters. The main complications included catheter occlusion (0-14.9%), catheter-related thrombosis (0-20.9%), and catheter-related bloodstream infection (0-0.96 per 1,000 catheter days). Conclusion MMCs demonstrate advantages in high success rate of insertion, prolonged dwell time, and manageable complications in adult patients with DVA. However, their widespread application requires further standardization of operational procedures, improvement of training systems, and conducting local health economic research.