Aim Defensive medicine refers to practices with low marginal benefit to patients that doctors may undertake to protect themselves from legal liability. We aimed to develop a scale to measure the practice of defensive medicine. Method We identified aspects of defensive medicine previously reported in the literature and conducted and analyzed semi-structured interviews with 21 physicians in Sakarya to augment and clarify these aspects between May 15, 2018, and June 15, 2018. Informed by these results, we developed, pilot tested, refined, and fielded a 10-item survey to 1724 doctors in Turkey between April 1, 2019, and July 16, 2019. We examined the psychometric properties of the scale using exploratory (EFA) and confirmatory factor analyses (CFA). Results The 10-item scale provided measures of 2 factors: positive defensive medicine (assurance) and negative defensive medicine (avoidance), with Cronbach’s alpha >0.8 for the scale and both subscales in both the EFA and CFA subsamples and excellent goodness-of-fit measures. Conclusions We developed a highly reliable scale to measure positive and negative defensive medicine practice that may be suitable for future research on physician decision making.