Masoud Shafiee told CNN security forces searched his apartment Tuesday and took him to Tehran's Evin prison for questioning. Evin prison was where his clients, Josh Fattal and Shane Bauer, were held for two years.
Shafiee said his files, including material on Fattal and Bauer's case, and his computer's hard drive were seized.
"I do not know what they were looking for," Shafiee said.
Fattal, Bauer and Sarah Shourd were arrested and accused of spying after crossing an unmarked border between Iraq and Iran in July 2009. Shourd was released on $500,000 bail in 2010. Bauer and Fattal were freed last week after a combined $1 million bail was posted. During the summer, Bauer and Fattal were convicted of spying and entering Iran illegally and each sentenced to eight years in prison.
The lawyer said he was questioned about the two hikers.
"They were very polite and respectful. But the very act of taking a lawyer to prison and searching his home just because he had done his duty seems excessive and reflects negatively on Iran's judiciary," Shafiee said.
Shafiee said he was asked to write a letter guaranteeing that he would appear in court whenever asked to do so before he was released.