Pituitary abscess (PA) is a rare but serious intrasellar disorder with potentially high disability and mortality. Secondary PA after transsphenoidal surgery (TS) is extremely rare, and only a few case reports have been identified in the literature. This study explored the salient clinical manifestations and etiologies to determine appropriate treatment. A retrospective review of 6832 consecutive patients who had undergone TS for pituitary diseases in Peking Union Medical College Hospital between 2003 and 2017 was performed. Demographics, previous medical and surgical history, clinical presentation, imaging features, and treatment details of 23 patients who had been diagnosed with secondary PA after TS among the cohort were reviewed. Among these patients, the original pituitary lesion before TS included Rathke's cleft cyst (8 patients, 34.8%), nonfunctioning pituitary adenoma (11 patients, 47.8%), and somatotropic adenoma (4 patients, 17.4%). The diameter of the original pituitary lesion ranged from 11 to 47 mm. About 52% of secondary PAs occurred within a half a year after surgery. Based on the history of TS, clinical presentation, biochemical testing, and typical imaging features, the preoperative diagnosis rate was as high as 78%. Although rare, secondary PA should be included in the differential diagnosis of intrasellar lesions after TS. Patients with an initial diagnosis of Rathke's cleft cyst or pituitary macroadenoma were more likely to have PA after TS. Adequate surgical drainage combined with microbiology-guided antibiotic therapy is the first choice for treatment.