The increase of antimicrobial resistance (AMR) is recognised as a threat for modern medicine and public health. Animal health and welfare rely on access to effective antimicrobials as well. To help control AMR, responsible use of antimicrobials is warranted and a decrease in inappropriate antimicrobial use (AMU) is necessary, both in human and veterinary medicine. The goal of the “Antimicrobial Stewardship and Pets” (ASAP)-project was to develop, implement and evaluate the effectiveness of an “antimicrobial stewardship programme” (ASP) to optimise antimicrobial use in Dutch companion animal clinics. The ASP was developed based upon recent literature, an interview study (with 18 Dutch companion animal veterinarians) and a survey study (completed by 350 companion animal veterinarians), and subsequently introduced in 44 Dutch companion animal clinics (2016-2018). The ASP used a multifaceted approach and consisted of, amongst others, post educational training, an information leaflet for companion animal owners and individual feedback per clinic. After introduction of the ASP, a significant decrease in AMU was observed (total AMU and in several subclasses of antimicrobials), on top of already ongoing changes in AMU prior to the project. Participants reported to be more aware of AMU after participation in the ASP and they could all mention practical changes that were made in daily practice. In a follow-up project, an e-learning module will be developed to be offered on a broader scale to more companion animal veterinarians, to optimise and to improve awareness on AMU.