The diversion of pseudoephedrine (PSE) into illicit drug markets is a major problem facing countries throughout the world. Domestic production of the illicit synthetic drug methamphetamine often relies on ‘drug runners’ obtaining PSE from community pharmacies that service the general public in a retail market. One approach to creating deterrence opportunities in this illicit market is the co-option of non-offending third parties to control or prevent diversion of PSE through Third-Party Policing (TPP). TPP relies on police partnerships with third parties, who use legal levers to target crime problems. In this paper, we describe a TPP partnership between police and pharmacies. The partnership draws on laws that require pharmacists to keep records and report retail sales of PSE to police. Using a survey of 620 community pharmacists from two Australian jurisdictions, we examine pharmacist observations of the regulations and the partnership, specifically their perceived ‘deterrent impact’ on preventing PSE diversion. We find that the TPP intervention enacted by pharmacists is a crucial mechanism to deter drug runners and prevent pharmaceutical diversion of PSE.