Background: A high thrombus burden has been connected with poor clinical events in patients with non-ST segment elevation myocardial infarction (NSTEMI). In patients with STEMI, a high MAPH score has been associated with a large thrombus burden. However, the predictive value of the MAPH score in determining the thrombus burden in patients with NSTEMI is unclear. The present report aimed to evaluate the prognostic role of the MAPH score in the estimating coronary thrombus burden in NSTEMI patients. The study patients were split into two groups according to their thrombus grade. The low shear rate (LSR) and high shear rate (HSR) were estimated by haematocrit levels and serum total protein levels. The MAPH score was calculated by adding mean platelet volume (MPV) levels and age, in addition to total protein and haematocrit. Results: The patients with a high thrombus burden (HTB) had a higher LSR, higher HSR and higher MAPH score compared to patients with low thrombus burden. MAPH score was found to be an independent predictors of HTB in Model 1 (OR: 1.124, 95% CI: 1.011–1.536; p = 0.039) and Model 2 (OR: 1.236; 95% CI: 1.002–1.525; p = 0.047). The cut-off value of the MAPH score for predicting HTB was 2 based on the Youden index. Conclusions: The MAPH score, which calculated by adding MPV levels and age, in addition to total protein and haematocrit, is a novel, easily accessible score. The MAPH score at both LSR and HSR was an independent predictor of HTB.