The Netherlands has been very successful in the last decade in reducing antimicrobial use in animals. On about a quarter of farms, antimicrobial use in weaned pigs remains relatively high. As Streptococcus suis ( S. suis ) infections are responsible for a high consumption of antimicrobials, a specific veterinary guideline to control S. suis was developed, but seemed to be poorly adopted by veterinarians. Guided by the theoretical domains framework, the aim of this study was to identify determinants influencing veterinarians’ adherence to this guideline. We interviewed 13 pig veterinarians. Interviewees described multiple approaches to managing S. suis problems and adherence to the guideline. Mentioned determinants could be categorized into 12 theoretical domains. The following six domains were mentioned in all interviews: knowledge, skills, beliefs about capabilities, beliefs about consequences, social influences, and environmental context and resources. The insights derived from this study are relevant for understanding factors influencing veterinarians’ adoption of scientific evidence and guidelines and can be used to develop evidence-based implementation strategies for veterinary guidelines.