AIMS/INTRODUCTION: Body fluid volume imbalance is common in patients with kidney failure, and is associated with all-cause mortality. This study aimed to investigate the association between fluid volume imbalance and albuminuria in patients with type 2 diabetes mellitus without kidney failure. MATERIALS AND METHODS: Using data from one cohort study, a baseline cross-sectional study of 432 participants and a longitudinal cohort study of 368 participants who could follow up was carried out. Body fluid imbalance was determined by measuring the extracellular water (ECW)-to-intracellular water (ICW) ratio (ECW/ICW) using bioelectrical impedance analysis. A change in the urinary albumin-to-creatinine ratio (ACR) was defined as the ratio of urinary ACR at follow up to that at baseline. The ECW/ICW ratio was compared with the level of albuminuria. RESULTS: In this cross-sectional study, the ECW/ICW ratio increased with the level of albuminuria. There was an association between the ECW/ICW ratio and logarithms of urinary ACR after adjusting for covariates (β = 0.205, P < 0.001). Furthermore, the ECW/ICW ratio was associated with a change in the urinary ACR after adjusting for covariates (β = 0.176, P = 0.004) in this longitudinal study. According to the receiver operating characteristic curve, the optimal cut-off point of the ECW/ICW ratio for incident macroalbuminuria, defined as ACR >300 mg/gCr, was 0.648 (area under the curve 0.78, 95% confidence interval 0.58-0.90). CONCLUSIONS: The ECW/ICW ratio is independently associated with the level of albuminuria in patients with type 2 diabetes mellitus without kidney failure. This reinforces the importance of monitoring fluid balance in patients with type 2 diabetes mellitus.