Background/Objectives: People with non-ST-segment elevation myocardial infarction (NSTEMI) with an occluded culprit vessel represent a unique subset of patients; however, their long-term outcomes remain unclear. This study aimed to compare 5-year mortality between NSTEMI patients treated with percutaneous coronary intervention (PCI) based on TIMI flow states in the culprit vessel on presentation (TIMI 0-1 compared to TIMI 2-3). Methods: A retrospective analysis of prospectively collected data of all NSTEMI patients who underwent PCI from 2012 to 2019 at a tertiary cardiac center (The Freeman Hospital, Newcastle-Upon-Tyne, UK) with follow up for 5 years until January 2024. Patients were identified from the database and categorized based on pre-procedural TIMI flow in the culprit vessel. A propensity score was used to pair TIMI 0-1 patients with a matched cohort of TIMI 2-3 patients. The primary outcome was 5-year all-cause mortality. Results: A total of 775 patients with TIMI 0-1 flow were matched with 750 patients who had TIMI 2-3 flow. Patients with TIMI 0-1 flow were more likely to have transient ST elevation (24% vs. 18%, p < 0.001) or Q waves (4% vs. 1%, p < 0.001) compared with patients who had TIMI 2-3 flow. They were also more likely to have moderately to severely impaired left ventricular systolic function compared with patients with TIMI 2-3 flow (21% vs. 16%, p = 0.01). In-hospital mortality (1.2% vs. 1.2%, p = NS), 1-year mortality (5% vs. 6.9%, p = NS), and 5-year mortality (16% vs. 18%, p = 0.34) were not significantly different between the two groups. The use of glycoprotein IIb/IIIa antagonists was associated with lower mortality, HR 0.64 (0.46 to 0.87). Conclusions: NSTEMI patients with occluded culprit vessels who underwent PCI had similar in-hospital and long-term outcomes to patients with patent culprit vessels. The use of glycoprotein IIb/IIIa inhibitors appears to be associated with lower mortality.