Background Intravenous unfractionated heparin (IV UFH) has a narrow therapeutic index and poses a high risk of bleeding. Objective To determine the impact of pharmacy monitoring and intervention on adherence to and appropriate implementation of IV UFH protocol. Setting A 438 bed hospital specializing in cardiac services. Methods This is a retrospective chart review study. Pre-pharmacy intervention data were collected from November 2013 to January 2014 and compared to post-pharmacy intervention data obtained between August 2014 and October 2014. Patients were included if they received IV UFH for at least 24 hours. The first three daytime laboratory draws were collected for each patient and analyzed using generalized estimating equations to quantify the association between pharmacy monitoring and adherence to the institution's protocol. Main outcome measures Designation of appropriate protocol, accurate selection of initial infusion rate, timing of anti-Xa levels within 60 min of anticipated due time, change of infusion rate within 120 min of laboratory result, and appropriate adjustment of infusion rates. Results A total of 195 data points were included. The initial selection of infusion rate and subsequent adjustments were more appropriate in the post-intervention period with an odds ratio of 8.36 (95% CI 2.41-29.01, p value = 0.0008), and 4.66 (95% CI 1.41-15.43, p value = 0.0118), respectively. Conclusion The results of this study indicate that pharmacy monitoring of IV UFH therapy has improved adherence to an institution's protocol and is associated with more accurate selection of initial infusion rates and adjustment of infusions based upon laboratory results.