Objective To study the impact of maternal country of birth on type-1-diabetes (T1D) therapy and outcome. Study Design and Methods 27,643 T1D patients aged ≤20 years with documented maternal country of birth from the multicenter German/Austrian diabetes patient registry (DPV) were analyzed. Patients were categorized based on their mother’s origin: Germany/Austria (reference), Turkey, Southern Europe, and Eastern Europe. To compare BMI standard deviation score (BMI-SDS), diabetes therapy and outcome between groups, multivariable regression was applied with adjustments for age, sex and duration of diabetes. Based on observed marginal frequencies, adjusted estimates were calculated. Linear regression was used for continuous data, logistic regression for binary data and Poisson regression for count data. All statistical analyses were performed using SAS 9.4. Significance was set at a two-tailed p<0.05. Results 83.3% of patients were offspring of native mothers. A Turkish, Southern or Eastern European background was documented in 2.4%, 1.7% and 4.3% of individuals. After demographic adjustment, patients with migration background had a higher mean BMI-SDS (Turkey, Southern Europe or Eastern Europe vs. Germany/Austria: 0.58±0.03, 0.40±0.04, or 0.37±0.02 vs. 0.31±0.01; ±SE) and a lower use of insulin pumps (26.8%, 27.9%, or 32.6% vs. 37.9%) compared to offspring of native mothers. Mean HbA1c was worst in individuals of Turkish mothers (Turkey vs. Germany/Austria: 69.7±0.7 vs. 66.6±0.1 mmol/mol; ±SE). Patients of Eastern European descent had an increased rate of severe hypoglycemia (22.09±0.13 vs. 16.13±0.02 events per 100 patient-years) and ketoacidosis was more prevalent in offspring of Turkish or Southern European mothers (7.50±0.10, or 7.13±0.11 vs. 6.54±0.02 events per 100 patient-years). Patients of Turkish descent were more often hospitalized (57.2±2.7 vs. 48.5±0.4 per 100 patient-years). All differences were significant. Conclusion The differences in diabetes therapy and outcome among patients with distinct migration background suggest that specific challenges have to be considered in clinical care.