Ridden by Victor Espinoza, the colt followed up his victory in the Kentucky Derby with a win by seven lengths in the pouring Maryland rain that turned the sandy course into a mud bath.
American Pharoah now needs to win the Belmont Stakes on June 6 to become the first horse since 1978 to complete the elusive Triple Crown.
“I told everybody the real American Pharaoh would show up today and indeed he did,” said Egyptian-born owner Ahmed Zayat. “He is the real deal for the sport, not for me, for the fans.
“I am hoping God, please let’s have another run at it. Hopefully we well see everyone at Belmont if he came out of the race well. He is the real deal and the sport needs him.”
For Mexican jockey Espinoza the Belmont will be another chance to win the Triple Crown. He rode California Chrome to victory in the Kentucky Derby and the Preakness last year before losing in the Belmont.
Since Steve Cauthen rose Affirmed to glory in all three races in 1978 there have been 13 times when a horse has gone into the Belmont with a chance of the Triple Crown – only to miss out.
American Pharoah, the 4-5 favourite, pulled clear just before turning into the stretch and the outcome was never in doubt from then on.
Tale of Verve was second and Divining Rod finished third.
American Pharoah paid $3.80, $3.40 and $2.80. Tale of Verve $19 and $8.80 and Divining Rod $5.20.
“He broke a little slow and I pushed him to go to front and as soon as I take the lead, that was it,” said Espinoza, who illustrated the conditions by pouring water out of his racing boot.
The win was the sixth Preakness triumph for trainer Bob Baffert, who was delighted.
“Just an incredible horse, what he does is amazing.
American Pharoah from day one people were expecting this and with the weather I was getting a little leery but great horses do great things and he showed it today,” Baffert said.
(Reporting by Simon Evans in Miami, editing by Gene Cherry)