Introduction When and how to intensify treatment in patients with type 2 diabetes (T2D) not achieving glycated hemoglobin (HbA1c) targets with oral antidiabetic drugs (OADs) in clinical practice remains a matter of clinical preference. This pilot study was conducted using the retrospective observational data from such patients to evaluate the impact on HbA1c of three treatment sequences: simultaneous initiation of basal insulin (BI) and a glucagon-like peptide-1 receptor agonist (GLP-1 RA; Cohort 1); BI followed by GLP-1 RA initiation within a 90-day timeframe (Cohort 2); or BI followed by GLP-1 RA initiation beyond 90 days (Cohort 3). Methods Data from the regional US electronic medical records database, Research Action for Health Network (REACHnet), were extracted for all patients with T2D aged >= 18 years who had encounter dates between January 2011 and August 2017 and >= 1 HbA1c laboratory value(s) < 90 days before BI initiation and >= 2 HbA1c laboratory values within 1 year after BI initiation and who met the inclusion criteria for GLP-1 RA initiation set for Cohorts 1, 2, or 3. The primary endpoints were the proportion of patients achieving HbA1c < 7.0%, which was estimated via Kaplan-Meier analysis, and change in HbA1c within 12 months. Results Overall, 869 patients were analyzed, of whom 109 were in Cohort 1, 301 in Cohort 2, and 459 in Cohort 3. Baseline HbA1c was 10.3 +/- 2.1, 10.3 +/- 2.0, and 10.2 +/- 2.1% for these three cohorts, respectively. Statistically significantly more patients in Cohort 1 than in Cohort 3 achieved HbA1c < 7.0% (33.4 vs. 20.9%, respectively; p = 0.0186). Mean observed reductions in HbA1c at 12 months were - 1.7% (Cohort 1), - 1.5% (Cohort 2), and - 1.3% (Cohort 3). Conclusions Simultaneous initiation of BI and GLP-1 RA achieves glycemic control more effectively than sequential initiation of BI with GLP-1 RA added beyond 90 days.