Background: Differences related to socioeconomic status (SES) in use of prehospital emergency medical services (EMS) have been reported. However, detailed data on potential disparities in the quality of the EMS according to SES are lacking. Methods: A nationwide cohort study of medical emergency calls made to the Danish emergency number 1-1-2 in the period 2016–2017. To measure quality of care, performance indicators from the Danish Quality Registry for Prehospital Emergency Medical Services were used. SES was based on income, education and adherence to workforce. Poisson regression was used to measure relative risk (RR). Results: We included 388,378 medical 1-1-2 calls, of which 261,771 were unique individuals; 42% of the calls concerned patients with low education, 5% concerned patients living in relative poverty and 23% concerned patients receiving social subsidy. There were no significant differences between the SES regarding time span for arrival of first EMS units. However, patients receiving social subsidy and retired people were more likely to be released at scene and to call again within 24 hours: Adjusted RRs were 2.79 [2.20; 3.54] and 2.08 [1.58; 2.75], respectively, compared with patients having a job. In addition, patients receiving social subsidy and retired people were more likely to call again within 24 hours after receiving telephone advice only: Adjusted RRs 2.35 [1.95; 2.82] and 1.88 [1.51; 2.35], respectively compared with patients having a job. Adjusted RRs for unplanned hospital contact after being treated and released at scene were higher for patients receiving social subsidy and retired people, respectively, relative to patients having a job. Conclusion: Patients with low SES were significantly more likely to contact the hospital or EMS again after their first call or after treatment and release at scene compared with patients with high SES. This indicates that callers with low SES did not receive the appropriate help.