Introduction: Insulin degludec (IDeg) is the longest-acting basal insulin available. Whether IDeg compared to shorter-acting basal insulins like insulin glargine U100 (IGlarU100) reduces the rate of diabetic ketoacidosis (DKA) in adolescents with type 1 diabetes is unknown. Objective: We hypothesized that adolescents with type 1 diabetes would have lower DKA rates and mean hemoglobin A1c (HbA1c) when using IDeg as compared to IGlarU100. Methods: To avoid selection bias, we used self-control case series methodology. Adolescents with type 1 diabetes treated for DKA from January 2015 through December 2018 who switched basal insulin from IGlarU100 to IDeg were eligible for analysis. Thirty-five patients were included, each acting as their own control. Mean HbA1c and DKA rate for the 12 months prior to and after switching to IDeg were compared. Results: Mean HbA1c prior to and after switching to IDeg was unchanged (97 ± 20 vs. 97 ± 21 mmol/mol [11.0 ± 1.8 vs. 11.0 ± 1.9%]). Median DKA rate (admissions/year) while on IGlar-U100 was 1 with an interquartile range (IQR) of 1-2. After switching to IDeg, median DKA admission rate remained 1, however the IQR decreased to 0-1 (one-sided p value 0.0004). Median change in DKA rate was 1 fewer admission per year, with a maximum reduction of 3 admissions. Higher baseline rates of DKA increased the odds of a patient reducing his/her DKA rate by 1 admission per year or more. Conclusions: Using IDeg for basal insulin in adolescent patients may decrease the rate of DKA relative to IGlarU100 despite no improvement in HbA1c and may be cost-effective.