A PCB official said that Rehman has been withdrawn from the Sialkot Stallions squad that would represent Pakistan in the Champions League qualifying tournament this month.
"We have been informed by the England and Wales Cricket Board that Rehman has failed a dope test taken in August while he was playing for Somerset in the English county championship," the official said.
He said that more details were being obtained from the ECB but what was confirmed was that Rehman faced penalties for failing the dope test.
"He has now returned to Pakistan and we will be taking his point of view soon after getting a detailed report from the ECB," he added.
PCB sources said that Rehman faced a ban now as his B sample has also come positive.
The experienced left-arm spinner was a key member of the Sialkot side, to be led by former captain Shoaib Malik.
The PCB official said that they were not aware as yet for what substance Rehman had failed the dope test.
"But being a member of the ICC and signatory to the World Anti-Doping Agency we will have to follow any penalties imposed by the ECB on him," the official added.
Last year Sri Lankan opener, Upul Tharanga was banned for three months after failing a dope test in the 2011 World Cup.
Tharanga was given a three-month ban by the International Cricket Council (ICC) after he appealed that he had unknowingly consumed the banned substance in an herbal remedy for curing an injury problem.