(1) Background: The association between microaxial flow pump (mAFP) timing and outcomes in acute myocardial infarction-related cardiogenic shock (AMI-CS) remains uncertain. (2) Methods: We conducted a retrospective single-center study of patients with AMI-CS admitted between January 2017 and July 2025. Prespecified 24 h landmark analyses included patients alive 24 h after intensive care unit (ICU) admission. The primary analysis compared patients with ST-segment elevation myocardial infarction (STEMI) receiving mAFP within 6 h with STEMI patients managed without temporary mechanical circulatory support (tMCS). Later STEMI implantation (>6–≤24 h) and both non-ST-segment elevation myocardial infarction (NSTEMI) timing cohorts were exploratory. The primary endpoint was subsequent in-hospital mortality from the landmark onward. Associations were assessed using multivariable logistic regression and propensity score-weighted models. (3) Results: In the primary STEMI cohort, 106 patients received mAFP within 6 h and 59 received no-tMCS. Subsequeunt in-hospital mortality was 17.0% versus 23.7%, respectively (p = 0.293). Early mAFP implantation was associated with lower mortality in the fully adjusted model (OR, 0.25 [95% CI, 0.06–0.99]; p = 0.048). Propensity score-based estimates were directionally consistent, with significance in the doubly robust weighted model (OR, 0.22 [95% CI, 0.06–0.85]; p = 0.028) but not in all weighted models. Later-timing and NSTEMI estimates did not reach statistical significance and were imprecise. (4) Conclusions: Among patients with STEMI who survived the first 24 h after ICU admission, mAFP implantation within 6 h was associated with lower subsequent in-hospital mortality. Exploratory later-timing and NSTEMI estimates were inconclusive. These observational findings are hypothesis-generating and require prospective validation.