Objective <p>This study evaluated the predictive value of serum homocysteine (HcY) and potassium ion (K⁺) for short-term prognosis of patients with acute cerebral infarction (ACI) undergoing intravenous thrombolysis with recombinant tissue plasminogen activator (rt-PA).</p> Methods <p>Totally, 140 ACI patients receiving intravenous thrombolysis using rt-PA were finally included and classified into early neurological deterioration (END) and non-END groups. Serum levels of HcY and electrolytes were detected. The 90-day prognosis of patients after thrombolysis was analyzed. Influencing factors for END and poor short-term prognosis in rt-PA-treated ACI patients were identified using stepwise regression models. Correlations of serum HcY and K⁺ with modified Rankin scale (mRS) scores were analyzed, and values of serum HcY and K⁺ in assessing END and poor prognosis of ACI patients were determined.</p> Results <p>The END group had higher age, atrial fibrillation, neutrophil ratio, CysC, FIB, FPG, TNF-ɑ, IL-6 and HcY levels, and National Institutes of Health Stroke Scale scores on admission but lower serum calcium ion and K⁺ concentrations than the non-END group. In ACI patients, serum HcY and K⁺ levels significantly correlated with mRS scores. Serum HcY and K⁺ levels were independent influencing factors for END and poor short-term prognosis of rt-PA-treated ACI patients. Combination of serum HcY and K⁺ could assist in predicting END and poor short-term prognosis in ACI patients.</p> Conclusion <p>Serum HcY and K⁺ levels are closely linked to END and short-term prognosis in ACI patients after intravenous thrombolysis using rt-PA and can be used as novel biomarkers for short-term prognosis in ACI patients.</p>