Background: Subarachnoid block (SAB) is a gold standard anesthetic technique for lower abdominal surgeries. Hypotension is a very common observation following a SAB. Perfusion index (PI) is a new parameter that can be used as a noninvasive method to find out the chances of developing hypotension after SAB. Aim and objective: The aim and objective of this study was find out the relation between baseline PI and the likelihood of developing hypotension after SAB in lower abdominal surgeries. Materials and methods: Our study was a prospective randomized observational study. In this study, patients were allocated in two groups according to the baseline PI. Group I includes patients with baseline PI ≤3.5 and group II includes patients with baseline PI > 3.5. Subarachnoid block with 15 mg 0.5% heavy bupivacaine at l4–l5 level or l3–l4 level intervertebral space was given and hypotension was mentioned as mean blood pressure <65 mm Hg. Results: The hypotension in group I was 12.28% whereas in group II was 74.58%. The receiver operating characteristic (ROC) curve showed that baseline PI could be a useful parameter for detecting patients at risk of developing hypotension. The area under the ROC curve for the prediction of hypotension was 0.912. The specificity and sensitivity of PI (baseline) of 3.3 to find hypotension were 75.38 and 94.12%, respectively. Conclusion: For predicting hypotension, PI can be used in patients having below umbilical surgeries under SAB. Therefore, it can be said that patients with PI (baseline) >3.5 have higher chances of developing hypotension than patients with PI <3.5.