Use of antimicrobials selects for antimicrobial resistance, and this poses a threat for both human and animal health. Although previous studies show that total antimicrobial use in Dutch companion animal clinics is relatively low and decreasing, the majority of antimicrobials prescribed are categorised as critically important for human medicine by the World Health Organization (WHO). Large differences in use between clinics are also observed. Identification of factors that influence the prescribing behaviour of veterinarians is needed to tailor future interventions aimed at promoting prudent use of antimicrobials in companion animals. The aim of this study was to explore factors influencing the antimicrobial prescribing behaviour of companion animal veterinarians in the Netherlands. Face-to-face, semi-structured interviews were used to interview 18 Dutch companion animal veterinarians. Interviews were held until theoretical data saturation was reached. An interview guide was used to structure the interviews, and ATLAS.ti 7.5 was used to manage and analyse the qualitative data. An iterative approach was applied to develop a conceptual model of factors that influence antimicrobial prescribing behaviour. The conceptual model shows four major categories of factors that influence the antimicrobial prescribing behaviour: veterinarian-related factors, patient-related (i.e. owner- and pet-related) factors, treatment-related factors (i.e. alternative treatment options and antimicrobial-related factors) and contextual factors (i.e. professional interactions, further diagnostics and environmental factors). All four major categories of influencing factors should be addressed to improve awareness on antimicrobial prescribing behaviour and to develop an antimicrobial stewardship programme for companion animal clinics.