Cardiac catheterization is useful in the diagnosis and treatment of congenital and acquired cardiac diseases. However, it is rarely done in Nigeria because of the limited cardiac catheterization laboratories in the country. Transforming the existing operating theaters to modified catheterization laboratories may bridge the gap of limited cardiac catheterization. This study reviewed the procedures, outcomes, and challenges of a modified catheterization laboratory in Nigeria. A retrospective review of all diagnostic cardiac catheterizations at the modified catheterization laboratory of Lagos State University Teaching Hospital (LASUTH) between January and May 2022 was performed. A total of 8 adult and 4 pediatric patients had cardiac catheterization, and the mean age was 23.7 ± 16.9 (range: 2 – 52) years. The most common lesion was the ventricular septal defect. Complex congenital heart disease was seen in 16% of subjects, whereas pulmonary hypertension was found in 83% (10). The most common complication was transient bradycardia. Good surgical outcome was recorded in the patients who subsequently had corrective surgeries. A modified catheterization laboratory may be a suitable alternative to the standard catheterization laboratory in low-resourced countries.