Background: Although blood urea nitrogen (BUN), creatinine (Cr) and electrolytes are not the mainstay of diagnosis in acute coronary syndrome (ACS) patients but they may have a role in providing a more detailed view of the complications and mortality rates. The aim of this study was to determine the efficacy of these parameters in the diagnosis and mortality risk-assessment of patients with ACS. Methodology: A total of 200 patients with ACS were recruited in this prospective study. The relationship of serum BUN, Cr and electrolytes with cardiac enzymes, Global Registry of Acute Coronary Events (GRACE) and mortality was assessed during a 6-months follow-up. Statistical test like multivariate linear regression and binary logistic regression analysis were applied. Results: On multivariate linear regression analysis, serum potassium (K) (Unstandardized Coefficient B = −3.77; p = 0.04) showed significant negative association with Creatine Kinease and serum BUN (Unstandardized Coefficient B = 0.52; p = 0.001) showed significant positive association with Troponin I. The patients with GRACE > 105 had significantly higher levels of serum BUN and Cr. Receiver operating characteristic curves showed that area under curve (AUC) of BUN (0.7) was higher than AUC of Cr (0.5). Multiple adjusted model showed that patients with BUN > 32.5 mg/dl were almost 20 times more likely to be associated with mortality as compared to reference group. Conclusion: In addition to cardiac enzymes, K along with BUN and Cr may serve as important aid in diagnosis of ACS. BUN and Cr may also serve as important tools in mortality-risk assessment of ACS patients. Keywords: Acute coronary syndrome, Blood urea nitrogen, Creatinine, Electrolytes, Potassium