The Japanese side were made to work hard for their victory by a Sepahan side determined to get revenge for their recent defeat in the AFC Champions League final.
However, the Reds got their noses in front shortly after the half-hour mark when Takahito Soma's inch-perfect cross found Yuichiro Nagai in the area and the No9 made no mistake from close range.
Shortly after the half-time interval Holger Osieck's charges doubled their advantage when Washington finished coolly from an acute angle after rounding Mohammad Savari in the Sepahan goal.
Urawa's No3 came in the 70th minute when Hadi Aghily scored his second own goal in as many games in the FIFA Club World Cup when he diverted a cross into his own net.
The Iranians, who had hit the post, prior to Urawa's second got the consolation their efforts deserved when Mahmoud Karimi scored ten minutes from time.