BACKGROUND: Immune checkpoint inhibitors (ICIs) are a central part of cancer therapy; however, cardiac complications, such as myocarditis, have the potential for significant morbidity and mortality. Within this population, the clinical significance of longitudinal strain (LS) remains unknown. OBJECTIVES: This study sought to define the changes in LS in ICI-treated patients, and their associations with high-sensitivity troponin I (hsTnI) and myocarditis. METHODS: We conducted a retrospective cohort study of patients who received ICIs at our hospital from April 2017 to September 2021. All patients underwent echocardiography and blood sampling at standardized time intervals. We measured the changes in global and regional LS before and after ICI administration. Age- and sex-adjusted Cox regression analysis was used to evaluate the association between LS and elevations in hsTnI and myocarditis. RESULTS: In a cohort of 129 patients with a median follow-up period of 170 (IQR: 62-365) days; 6 and 18 patients had myocarditis and hsTnI elevation, respectively. In an age- and sex-adjusted Cox proportional hazards model, an early relative worsening of ≥10% in the basal and mid LS and ≥15% in global LS was associated with hsTnI elevation. Relative reductions in LS were not significantly associated with myocarditis; however, 4 of the 6 patients with myocarditis had relative reduction of ≥10% in the basal LS. CONCLUSIONS: An early worsening in the global and regional LS was associated with increased hsTnI in patients receiving ICIs. Assessment of LS early after ICI administration should be further studied as a strategy for risk stratification of ICI-treated patients.