Abstract Aims The aim of this study was to investigate the efficacy and safety of ticagrelor monotherapy in patients undergoing percutaneous coronary intervention (PCI) stratified according to the baseline white blood cell (WBC) count. Methods and results This is a post hoc analysis of the GLOBAL LEADERS trial, a multi-centre, open-label, randomized all-comer trial in patients undergoing PCI, comparing the experimental strategy (23-month ticagrelor monotherapy following 1-month dual anti-platelet therapy [DAPT]) with the reference strategy (12-month aspirin monotherapy following 12-month DAPT). Patients were stratified into two WBC groups, either < or ≥median WBC count of 7.8 × 109 cells/L (lower or higher WBC group, respectively). The primary endpoint was a composite of all-cause mortality or new Q-wave myocardial infarction at 2 years. Of 14 576 patients included in the present study, 7212 patients (49.5%) were classified as the lower WBC group, who had a significantly lower risk of both ischaemic and bleeding outcomes at 2 years. At 2 years, the experimental strategy was associated with a significant lower incidence of the primary endpoint compared with the reference strategy in the lower WBC group [2.8% vs. 4.2%; hazard ratio (HR): 0.67; 95% confidence interval (CI): 0.52–0.86] but not in the higher WBC group (4.8% vs. 4.7%; HR: 1.01; 95% CI: 0.82–1.25; Pinteraction=0.013). There were no significant differences in the risks of Bleeding Academic Research Consortium type 3 or 5 bleeding between two anti-platelet strategies regardless of the WBC groups. Conclusion Increased WBC counts, which may reflect degree of inflammation, at the time of index procedure may attenuate the anti-ischaemic benefits of ticagrelor monotherapy observed in patients with lower WBC counts.