The 25-year-old Spaniard suffered a ligament tear in his right knee during West Ham’s 2-0 FA Cup defeat at Wigan Athletic last month.
“Pedro has undergone surgery to repair the medial collateral ligament, and we’re delighted with how it went,” West Ham’s head of medical services Gary Lewin said in a statement.
“He went to a specialist in Barcelona for the operation and he is in the best possible hands as the rehab process gets underway.
“Pedro is likely to be out for a little while, but we are confident that he will return fit and strong in ample time for pre-season.”
— West Ham United (@WestHamUtd) February 6, 2018
Obiang has made 86 appearances for West Ham since arriving from Italian club Sampdoria in 2015