Chang announced his candidacy for the December 2001 legislative elections in March 2001. One of his opponents in the December 2001 elections was his alleged 1999 mistress, but she received only a fraction of his eventual winning vote count. From 2002 through 2012, he was a member of the Legislative Yuan, first representing the constituency of Taipei City South from 2002 to 2005 and then representing Taipei City North from 2005 through 2012. He served as the Chairman of Interior Affairs Committee while in the legislature.