In 1990, he was appointed Chairman of Committee Supreme Soviet of RSS Moldavia for State Security and Military Affairs, and in September 1990—a member of the Presidential Council of the Republic of Moldova.

20 of 5 February 1992, Division General Ion Costaș was appointed as the first Minister of Defence of the Republic, but was dismissed (along with Anatol Plugaru, Security Minister) after Moldovan troops lost the fighting to restore part of Moldova Transnistria against Transnistrian paramilitary troops and 14th Russian Army, led by General Aleksandr Lebed.

On 24 February 2010, the Minister of Internal Affairs, General Victor Catan, Gen. Ion Costaș was decorated with "The Cross of Merit", the highest distinction of the MIA with occasion of celebrating of his birthday.

He led the contingent of veterans of the Transnistrian War on Great National Assembly Square during the 2011 Chișinău Independence Day Parade.

[2][3] However, on 29 September, Costaș announced that he would withdraw his candidacy due to the "violation by state institutions of the constitutional provisions regarding the election of the president" and urged other candidates to do the same.