Objective Cross-sectional studies found that higher levels of the novel adipokine omentin-1 were associated with higher adiponectin and lower levels of risk factors for type 2 diabetes, but its relevance for incident type 2 diabetes is currently not understood. Therefore this study investigated whether serum omentin-1 was associated with changes in glycaemia and incident type 2 diabetes independently of adiponectin. Design and methods The study was based on participants aged 62–81 years from the population-based Cooperative Health Research in the Region of Augsburg (KORA) F4/FF4 cohort. Associations of baseline serum levels of omentin-1 and adiponectin with changes in glycaemia were assessed in 471 non-diabetic participants, and associations between both adipokines and incident type 2 diabetes were assessed in 76 cases and 430 non-cases (follow-up time 6.5 years). Multivariable linear and logistic regression models were adjusted for multiple potential confounders. Results Higher serum levels of omentin-1 were associated with increases in fasting glucose, 2-h glucose and HbA1c (all P < 0.001) and with incident type 2 diabetes (adjusted odds ratio (OR) (95% CI): 1.40 (1.03; 1.90) per s.d. of log₂-transformed omentin-1; P = 0.032). These associations were independent from adiponectin levels, which showed associations with changes in glycaemia and risk of type 2 diabetes in the opposite direction. We found no statistically significant interactions of omentin-1 with adiponectin or sex in the association with incident type 2 diabetes (all P > 0.1). Conclusions Systemic levels of omentin-1 were positively associated with increases in glycaemia and incident type 2 diabetes in this older population. These associations were independent of potential confounders including adiponectin.