Background: Chronic kidney disease is a frequent comorbidity among patients with acute coronary syndrome (ACS). We aimed to evaluate treatment characteristics in ACS patients according to their renal function and to assess the effect of differences in therapy on clinical outcomes. Methods: Included were patients with ACS enrolled in the biennial Acute Coronary Syndrome Israeli Surveys (ACSIS) during 2000-2013. Excluded were patients with cardiogenic shock at presentation. The estimated glomerular filtration rate (eGFR) was calculated using the simplified Modification of Diet in Renal Disease (MDRD) formula. The distribution of the eGFRs was divided into 4 categories (<45, 45-59.9, 60-74.9, and ≥75 mL/min/1.73 m2). The primary endpoint was all-cause mortality at 1 year. Results: A total of 13,194 patients with ACS were included. Patients with a reduced eGFR were less likely to be admitted to a coronary care unit and had lower rates of coronary angiograms and subsequent percutaneous coronary interventions. Furthermore, as the eGFR was lower, the patients were less frequently treated with aspirin, clopidogrel, β-blockers, and ACE inhibitors/angiotensin receptor blockers. We demonstrated an inverse association between renal function and 1-year mortality, with the highest mortality rates observed in the group with the lowest eGFR (HR = 3.8, 95% CI 2.9-4.9, p < 0.0001). Differences in mortality remained significant following a multivariate analysis for all the baseline characteristics as well as for invasive and medical treatment (HR = 2.7, 95% CI 1.9-3.7, p < 0.0001). Conclusions: ACS patients with chronic kidney disease represent a high-risk group with an increased mortality risk. Despite this high risk, these patients are less frequently selected for an invasive treatment strategy and are less commonly treated with guideline-based medications. However, reduced renal function was associated with higher mortality regardless of the variations in therapy.