Background: The role of deferred vs immediate stenting during primary percutaneous coronary intervention (PCI) for patients with ST-segment elevation myocardial infarction (STEMI) remains controversial. Methods: We undertook a collaborative meta-analysis of study-level data by searching electronic scientific databases for investigations of primary PCI patients randomized to deferred or immediate stenting and subsequent cardiac magnetic resonance imaging. Primary angiographic and imaging outcomes were slow/no-reflow and microvascular obstruction (MVO), respectively. Main secondary outcome was recurrent ischemia. Results: Among 4 trials, a total of 1570 patients with STEMI were assigned to primary PCI with either deferred (n = 779) or immediate stenting (n = 791). Of these, 797 participants had analyzable cardiac magnetic resonance imaging examinations. Median clinical follow-up was 9 months. Patients treated with deferred stenting showed a lower risk of developing slow/no-reflow in the culprit vessel (risk ratio [RR], 0.54 [95% confidence interval (CI), 0.41-0.72]; P < 0.001), a similar risk for MVO (RR, 0.93 [95% CI, 0.76-1.14]; P = 0.51), and trended higher in the risk of recurrent ischemia (RR, 2.42 [95% CI, 0.88-6.63]; P = 0.09) compared with those treated with immediate stenting. The treatment effect for slow/no-reflow and MVO correlated with a thrombus score grade > 3 at the baseline angiography and with the total stent length implanted in the culprit artery. Conclusions: A strategy of deferred stenting during primary PCI improves angiographic but not imaging or clinical outcomes compared with immediate stenting. The potential lower risk for myocardial injury by deferred stenting in primary PCI patients with STEMI and high thrombus burden requires a confirmation in adequately sized randomized trials.