Aims: This study aimed to investigate whether the single-nucleotide polymorphism (SNP) rs2910164 residing within microRNA-146a (miR-146a) is associated with diabetic microvascular complications diabetic nephropathy (DN), proliferative diabetic retinopathy (PDR) or diabetic macular oedema (DME) in either Caucasian patients with type 1 (T1DM) or type 2 (T2DM) diabetes mellitus. Methods: Caucasian patients with T1DM (n = 733) or T2DM (n = 2215) were recruited from ophthalmology, renal and endocrine clinics in Australia and the UK. Patients with T2DM were required to have diabetes mellitus (DM) for at least 5 years and be on treatment with oral hypoglycaemic drugs or insulin. In total, 890 participants had DN (168 with T1DM and 722 with T2DM), 731 had PDR (251 with T1DM and 480 with T2DM) and 1026 had DME (170 with T1DM and 856 with T2DM). Participants were genotyped for SNP rs2910164 in miR-146a. Analyses investigating association were adjusted for relevant clinical covariates including age, sex, DM duration, Hb A1c and hypertension. Results: A significant association was found between the C allele of rs2910164 and DN in the T1DM group (OR 1.93; CI 1.23–3.03; P = 0.004), but no association found in the T2DM group (OR 1.05; CI 0.83–1.32; P = 0.691). In the subset of T2DM patients, the C allele was specifically associated with DME (OR 1.25; CI 1.03–1.53; P = 0.025). No association with DME was found in the T1DM group (OR 0.87; CI 0.54–1.42); P = 0.583), or with PDR for either type of DM. Conclusions: Rs2910164 is significantly associated with microvascular complications DN in patients with T1DM and DME in patients with T2DM.