Mikulic's brother Davor told Hina Damir was fine although he found detention hard because his inability to speak any foreign language made communication in the camp impossible.
According to Davor, his brother said he did not know if he would be able to telephone the family again.
Mikulic was arrested over a month ago by U.S. troops in Iraq on suspicion of espionage. He was detained at Bucca camp near Umm Qasr in southern Iraq, where U.S. troops detain foreigners.
The Americans have promised Croatian authorities they will expedite the Mikulic case, adding the case is being considered by an official body comprised of Iraqi and foreign citizens who are not members of the U.S. army.