BACKGROUND: Although detection of microscopic hematuria is a well-known diagnostic method for urolithiasis, its ability to predict urolithiasis treatment outcomes in adults is unknown. OBJECTIVE: To evaluate the role of microscopic hematuria in conservative treatment of ureteral calculus. DESIGN, SETTING, AND PARTICIPANTS: This cohort study involved 482 patients who were diagnosed with a single uncomplicated ureteral calculus (≤10 mm) using computed tomography and underwent conservative therapy at two Japanese community hospitals between 2013 and 2018. Patients were divided into three groups according to the severity of microscopic hematuria (no, ≤4; mild to moderate, 5-99; and severe, ≥100 red blood cells per high-power field) and as determined during the first emergency department or urologic outpatient clinic visit. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: A multivariate logistic regression analysis was performed to estimate the odds ratio for successful conservative therapy at 28 d after the diagnosis. Statistical significance was set at p < 0.05. RESULTS AND LIMITATIONS: Of the 482 patients, 81 (16.8%), 209 (43.4%), and 192 (39.8%) had no, mild to moderate, and severe microscopic hematuria, respectively. After adjustments for six relevant confounders, severe microscopic hematuria showed a significant association with successful conservative therapy at 28 d (adjusted odds ratio, 1.91; 95% confidence interval, 1.02-3.57; p = 0.043), whereas mild to moderate microscopic hematuria did not (adjusted odds ratio, 1.05; 95% confidence interval, 0.57-1.93; p = 0.872) when compared with no microscopic hematuria. CONCLUSIONS: Severe microscopic hematuria was significantly associated with successful conservative therapy for single uncomplicated ureteral calculus. PATIENT SUMMARY: Microscopic hematuria might have predictive value for conservative treatment of a single uncomplicated ureteral calculus. Using the presence or absence of blood in urine and other predictive factors, clinicians may lead patients with a single uncomplicated ureteral calculus to successful conservative therapy.