Background Cardiac catheterization is usually done routinely in patients with univentricular hearts before palliative Bidirectional Glenn (BDG) surgery. The objective of this study was to compare the outcomes of patients with physiological univentricular hearts and restrictive pulmonary flow that did not undergo routine cardiac catheterization before BDG with the patients that did have cardiac catheterization done. We retrospectively reviewed the data of all patients with single ventricle physiology and restrictive pulmonary blood flow who underwent BDG surgery from January 2016 till December 2020. Patients were divided into two groups: the catheterization and the non-catheterization groups. Results Out of 93 patients, 25 (27%) underwent BDG surgery without prior cardiac catheterization. The median age of patients was ten months, interquartile range (IQR) was 5–18 months. Tricuspid atresia represented 36% of the non-catheterization group, while unbalanced atrioventricular septal defect and hypoplastic left heart syndrome represented 19% and 17.6% of the catheterization group. No patients in the catheterization group were excluded from further BDG surgery based on the catheterization data. Moreover, no significant differences were found between the patients' groups regarding the length of hospital stay, length of intensive care unit stay, postoperative oxygen saturation, or survival (P = 0.266, P = 0.763, P = 0.543, P = 0456). Conclusions Although pre-BDG cardiac catheterization is the routine and standard practice, in certain situations, some patients with single ventricle physiology and restrictive pulmonary blood flow may go directly to BDG without cardiac catheterization if noninvasive imaging is satisfactory on a case-by-case basis and according to center experience. Pre-BDG catheterization could be reserved for patients with limited echocardiographic studies, high-risk patients, or those indicated for catheter intervention before BDG surgery.