Valentyna Telychenko, a lawyer representing Gongadze's widow, said Myroslava Gongadze would take the case to the Strasbourg-based European rights court.
Ukraine's Higher Special Court on June 26 upheld a lower court decision to drop charges against Kuchma.
Heorhiy Gongadze, an investigative journalist, disappeared in September 2000. His headless body was found two months later.
Kuchma, who was president from 1994 to 2005, was charged with exceeding his authority in issuing orders to his subordinates that ultimately led to Gongadze's killing.
Kuchma denies any involvement in the murder.