This field experiment investigates the effect of first-time inspections of restaurants’ waste sorting and explores whether motivational interviewing (MI) training of inspectors in this specific setting enhances the propensity of restaurants to be compliant with regulations. Our results show strong positive effects of first inspections with an average improvement of 55%. Also, the MI training of inspectors seems to affect compliance. However, this may also be a combined effect of the first inspection, MI training and more days between inspections. Further research is needed.