Objectives Pancreatic fistula after distal pancreatectomy (DP) remains an unsolved problem, and postoperative CT imaging often demonstrates fluid collection (FC) around the pancreatic remnant. This study sought to clarify the clinical implications of FC. Methods This study enrolled 146 patients who underwent DP. FC was defined as a cyst-like lesion C 10 mm in diameter on CT imaging at postoperative day (POD) 7. FC size, irregularity of FC margin, and air bubbles in FC were investigated. In addition, clinical data were retrospectively collected, and useful predictive factors for postoperative pancreatic fistula (POPF) were analyzed. Results Clinically relevant POPF was observed in 26 patients (17.8%), and FC was detected in 136 patients (94.4%). Multivariate analysis identified FC size and drain amylase levels on POD3 as significant risk factors for POPF. Cutoff values were determined by ROC analyses, and the levels of the FC size and drain amylase on POD3 were determined as 41 mm and 1026 IU/L, respectively. The sensitivity and specificity of FC diameters [ 41 mm were 76.9% and 75.0%, respectively, while those of drain amylase levels [ 1026 IU on POD3 were 73.1% and 75.8%, respectively. Conclusions While treating some FCs after DP was necessary for the management of POPF, others did not require any intervention since most of them spontaneously disappeared. FC size and drain amylase levels on POD3 were found to be significantly associated with POPF and could potentially help to determine appropriate treatment.