Background: Anthracyclines form the backbone of many systemic chemotherapy regimens but are accompanied by dose-limiting cardiotoxicity. We elucidate the progression and severity of cardiac function over time, in the absence of cardioprotection, which less is known about. Methods: This PRISMA-guideline-adherent review was registered on PROSPERO (CRD42022373496). Results: 26 studies met the eligibility criteria including a total of 910 patients. The overall reduction in post-anthracycline pooled mean left ventricular ejection fraction (LVEF) in placebo arms of the included randomised-controlled trials was 4.5% (95% CI, 2.6 to 6.4). The trend in LVEF showed a progressive decline until approximately 180 days, after which there was no significant change. Those receiving a cumulative anthracycline dose of 300 mg/m2 experienced a more profound reduction. The overall pooled risk of a 10% absolute decline in LVEF from baseline, or a decline to an LVEF below 50%, was 17% (95% CI: 11 to 24; I2 = 71%). Sensitivity analyses of baseline LVEF and trastuzumab treatment status did not yield significant differences. Conclusion: While the mean LVEF decline in patients without cardioprotective therapy was clinically small, a vulnerable subset experienced significant impairment. Further research to best identify those who benefit most from cardioprotective therapies when receiving anthracyclines is required.