Background Elevated serum phosphorus levels may be associated with adverse outcomes in cardiovascular disease. This study aimed to investigate the relation between serum phosphorus levels and risk of all-cause mortality in Chinese patients with ST-segment elevation myocardial infarction (STEMI) who had preserved renal function at baseline. Methods We enrolled patients with STEMI who had preserved renal function at baseline in Xuanwu Hospital from January 2011 to December 2016. Those patients were divided into four groups based on serum phosphorus levels. All-cause mortality rates were compared between groups. Mean duration of follow up was 54.6 months. We used Cox proportional-hazards models to examine the relation between serum phosphorus levels and all-cause mortality after adjustment for potential confounders. Results 1989 patients were involved and 211 patients (10.6%) died during follow-up. Based on serum phosphorus levels, patients were categorized into the following groups: < 2.50 mg/dL (n = 89), 2.51-3.50 mg/dL (n = 1066), 3.51-4.50 mg/dL (n = 672) and > 4.50 mg/dL (n = 162), respectively. The lowest mortality occurred in patients with serum phosphorus levels between 2.51-3.50 mg/dL, with a multivariable-adjusted hazard ratio of 1.19 (95% CI: 0.64-1.54), 1.37 (95% CI: 1.22-1.74), and 1.46 (95% CI: 1.35-1.83) in patients with serum phosphorus levels of < 2.50 mg/dL, 3.51-4.50 mg/dL and > 4.50 mg/dL, respectively. Conclusions Elevated serum phosphorus levels were associated with all-cause mortality in Chinese patients with STEMI who had preserved renal function at baseline.