Objectives: To evaluate the influence of low socioeconomic status (SES) on mortality among patients with granulomatosis with polyangiitis (GPA). Methods: Using nationwide registers, we established a cohort of 827 patients diagnosed with GPA in the public hospital system of Denmark. For each patient, information regarding educational level, civil status, employment status, and comorbidities at time of GPA diagnosis was collected. We used Cox regression analyses to calculate hazard ratios (HRs) adjusted for age, gender, calendar period of GPA diagnosis, and Charlson Comorbidity Index score for preceding illnesses as a measure of relative risk of death. We assessed the risk of death associated with three measures of low SES: basic schooling only, civil status as single, and being unemployed or recipient of disability pension. Results: The median age of patients at GPA diagnosis was 61 (interquartile range 51–69) years, and 508 were 18–64 years old. During a total of 4337 person-years, 237 patients died. Among patients aged 18–64 years at GPA diagnosis, all three measures of low SES were identified as risk factors for death [basic schooling only: HR = 2.04, 95% confidence interval (CI) 1.30–3.19; civil status as single: HR = 1.95, 95% CI 1.24–3.05; being unemployed or recipient of disability pension: HR = 2.96, 95% CI 1.72–5.08]. The association between low SES and mortality was less pronounced among patients aged ≥ 65 years. Conclusions: Our observations indicate that low SES is associated with increased mortality in GPA, especially among patients of working age.