OBJECTIVE Portal hypertension (PHT) due to extrahepatic portal venous obstruction (EHPVO) is common in developing countries. Hypersplenism is a near-constant feature of EHPVO, but its significance, unlike in cirrhotics, is unknown. We aimed to study the relationship between hypersplenism and the severity of PHT in patients with EHPVO. METHODS This prospective study was done at a tertiary care center from January 2014 to August 2015. All patients with EHPVO who underwent a splenectomy and a shunt or devascularization were included. Data regarding clinical profile, preoperative parameters, and intraoperative details were recorded. The correlation was studied between hypersplenism and the intraoperatively measured portal pressures and markers of PHT. RESULTS Of the 40 patients studied (mean [SD] age 22.4 [8.4] years), hematological hypersplenism was present in 39 (97.5%). The mean (SD) hemoglobin, total leukocyte counts (TLC), and platelet counts were 9.9 (2.4) g/dL, 2971 (1239) cells/mm3, and 66,400 (32047) cells/mm3, respectively. The mean (SD) sonographic spleen volume (SV), splenic weight, and intraoperative portal pressure were 1084.7 (553.9) cm3, 1088.7 (454.7) g, and 35.6 (5.1) mmHg, respectively. The TLC and platelet counts correlated inversely with the portal pressure. Additionally, the platelet counts correlated negatively with eradicated variceal status, SV, and weight; hemoglobin with SV and weight; and TLC with SV. Multivariate analysis showed the platelet counts were an independent predictor of portal pressures and platelet counts ≤ 53,500 cells/mm3 indicated significantly high portal pressures. CONCLUSIONS The platelet counts showed a significant inverse correlation with portal pressures in patients with EHPVO and may be used as surrogate markers of PHT. A platelet count ≤ 53,500 cells/mm3 is predictive of significantly high pressures.