OBJECTIVES: The aim of this study was to evaluate the impact of missed clinic appointments on the time in therapeutic international normalized ratio range (TTR) in an inner-city underserved minority population. METHODS: A cross-sectional survey and cohort study were conducted in patients treated with warfarin and managed at the University of Illinois at Chicago Antithrombosis Clinic. Patient social, demographic, and clinical characteristics were compared using parametric and non-parametric tests as appropriate and weighted linear regression using propensity scores was performed to identify the association between patients with ≥ 15% missed clinic appointments and TTR. RESULTS: A total of 291 consecutive patients responded to the survey and were included in the study. Patients with ≥ 15% missed clinic appointments had lower mean age (51.36 ± 17.62 vs. 57.18 ± 16.97, p = 0.0051), lower TTR (44.97 ± 19.63 vs. 53.25 ± 20.36 p = 0.0007), a higher number of total clinic appointments for monitoring (21.25 ± 8.37 vs. 16.28 ± 7.73, p = <0.0001), higher non-adherence with warfarin therapy (16.10 ± 14.02 vs. 10.22 ± 12.85, p = <0.0001) and longer duration of therapy (4.38 ± 5.91 years vs. 2.71 ± 3.26 years, p = 0.0009) compared to patients with < 15% missed clinic appointments. Based on the results of the unadjusted bivariate regression model, patients with ≥ 15% missed clinic appointments had significantly lower TTR (β = -8.43, 95% CI: -13.10, -3.76, p = 0.0004). After adjusting for confounders using inverse probability weights, the association between missed clinic appointments and TTR remained significant (β = -6.30, 95% CI: -11.18, -1.42, p = 0.0115). CONCLUSIONS: Missed clinic appointments for anticoagulation management negatively affected the quality of anticoagulation control. Future studies should evaluate factors associated with missed clinic appointments and the feasibility of more accessible high-quality models of care in underserved minorities.