AimTo compare the effectiveness of different basal insulins (BI) prescribed as an add‐on to or switch from glucagon‐like peptide‐1 receptor agonist (GLP‐1 RA) therapy.Materials and MethodsRetrospective, real‐world data from electronic medical records of 32 Italian diabetes clinics were used, after propensity score adjustment, to compare effectiveness after 6 months of treatment with second‐ versus first‐generation BI (2BI vs. 1BI) or glargine 300 U/ml versus degludec 100 U/ml (Gla‐300 vs. Deg‐100), when added to (ADD‐ON) or in substitution of (SWITCH) GLP‐1 RA. Only comparisons, including a minimum of 100 patients per group, were performed to ensure adequate robustness of the analyses.ResultsIn the ADD‐ON cohort (N = 700), greater benefits of 2BI versus 1BI were found in glycated haemoglobin {HbA1c; estimated mean difference: −0.32% [95% confidence interval (CI) −0.62; −0.02]; p = .04} and fasting blood glucose [FBG; −20.73 mg/dl (95% CI −35.62; −5.84); p = .007]. In the SWITCH cohort (N = 2097), greater benefits of 2BI versus 1BI were found in HbA1c [−0.22% (95% CI −0.42; −0.02); p = .03], FBG [−10.15 mg/dl (95% CI −19.04; −1.26); p = .03], and body weight [−0.67 kg (95% CI −1.30; −0.04); p = .04]. In the SWITCH cohort starting 2BI (N = 688), marked differences in favour of Gla‐300 versus Deg‐100 were documented in HbA1c [−0.89% (95% CI −1.26; −0.52); p < .001] and FBG [−17.89 mg/dl (95% CI −32.45; −3.33); p = .02]. Using propensity score matching as a sensitivity analysis, the benefit on HbA1c was confirmed [−0.55% (95% CI –1.02; −0.08); p = .02]. BI titration was suboptimal in all examined cohorts.Conclusions2BI are a valuable option to intensify GLP‐1 RA therapy. Switching to Gla‐300 versus Deg‐100 was associated with greater HbA1c improvement.