Saharkhiz was detained in mass arrests following the disputed presidential election in June 2009.
Ebadi told RFE/RL on August 29 that in her letter she asks the UN high commissioner, Navi Pillay, to take up Saharkhiz's case.
Ebadi said she believes that cases of abuse of human rights in Iran can and should be considered outside of the country, too, and even in international courts.
She said Saharkhiz had complained about prison conditions and his "illegal arrest by Iranian authorities."
On July 25 Saharkhiz had warned that if his complaint against several members of the Iranian government is not pursued, he would appeal to international bodies.
Ebadi told RFE/RL that Saharkhiz's family says his health has worsened and that he is confined to a wheelchair after being tortured in prison.
"I could not personally meet Mr. Saharkhiz as I am outside Iran. However, I have contact with Nasrin Sotoudeh, Mr. Saharkhiz's lawyer in Iran, and she told me that Mr. Saharkhiz's condition is bad," Ebadi tells RFE/RL. "She also confirmed [the authenticity of] Mr. Saharkhiz's letter to me from Evin prison, which was published on some websites.”
Ebadi said she hopes her letter to the United Nations will be effective and force the Iranian government to live up to its international obligations.
"Some day, the Iranian authorities have to let United Nations human rights rapporteurs go to Iran for inquiries. This letter asks that officials be allowed to meet prisoners like Mr. Saharkhiz, and not only Iranian officials."
Iran's judiciary has yet to issue a verdict in Saharkhiz's case.
Earlier this month, Saharkiz filed a lawsuit against Nokia Siemens, accusing the company of delivering surveillance equipment to Iran that helped the authorities trace his whereabouts through his cell phone.