Purpose: Type 2 diabetes mellitus (T2DM) can lead to microvascular complications including diabetic kidney disease. Albuminuria is an important marker to diagnose kidney injury in T2DM patients and healthy sleep duration is important for maintaining good health in patients with T2DM. However, the association between sleep duration and albuminuria in T2DM patients is unclear. Thus, this study aimed to investigate the association between sleep duration and albuminuria in patients with T2DM in Ningbo, China. Methods: A cross-sectional study was conducted at National Metabolic Management Centre (MMC)- Ningbo First Hospital from March 2018 to February 2021. Adult patients with T2DM were included in the study. The sleep duration (daytime and nocturnal) was self-reported. Albuminuria was defined as the presence of urinary albumin-creatinine ratio ≥30 mg/g. Logistic regression analyses were performed to identify the association. Results: There were 2688 T2DM patients in the study. In the unadjusted model (1), the odds of albuminuria increased with the daytime sleep duration (31–60 minutes: OR 1.36, 95% CI 1.09–1.71; ≥61 minutes: 1.73, 1.33–2.24). Similarly, after adjusting for age and sex (model 2), the odds of albuminuria increased with the daytime sleep duration (31–60 minutes: 1.34, 1.07–1.68; ≥61 minutes: 1.69, 1.30–2.20). After adjusting for age, sex, physical activity, smoking, alcohol drinking, overweight/obesity, hypertension, hyperuricaemia, duration of T2DM, glycated haemoglobin, angiotensin-converting enzyme inhibitors/angiotensin receptor blocker usage and nocturnal sleep duration (model 3), the odds of albuminuria increased with the daytime sleep duration (31–60 minutes: 1.33, 1.04–1.71; ≥61 minutes: 1.71, 1.29–2.26). However, no relationship was found between nocturnal sleep duration and albuminuria. Conclusion: Longer daytime sleep is found to be associated with albuminuria in patients with T2DM in Ningbo, China but no association is found between nocturnal sleep duration and albuminuria. The findings are exploratory, and there is a need for longitudinal studies on this topic.