Aims: This study sought to analyze the association of social isolation and loneliness with the risk of type 2 diabetes onset. Methods: Two authors systematically searched PubMed, EMBASE, and Web of Science databases for studies published until February 2025, assessing the risk of incidence of type 2 diabetes in individuals who are socially isolated or lonely. To quantify the risk of incident diabetes, hazard ratios (HR) for loneliness and social isolation were pooled using a random-effects inverse-variance model with empirical Bayes estimation. Results: Nine prospective cohort studies were included, comprising 1,112,887 individuals (60.5 % female, mean age = 57.1 years), with 50,961 new cases of type 2 diabetes over a mean follow-up of 10.7 years. Loneliness was associated with a 32% increased risk of type 2 diabetes (HR = 1.32 [95 % confidence interval [CI]:1.11-1.57]). Social isolation was linked to a 20% higher risk (HR = 1.20 [95 %CI:1.01-1.43]). The included studies showed fair-to-good methodological quality (mean score: 10.11/14) based on the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Conclusions: Social isolation and loneliness are significant risk factors for type 2 diabetes. Addressing social connectedness could be a valuable strategy for diabetes prevention, emphasizing the need to incorporate psychosocial factors into public health initiatives.