Church Cooperation (CC) is a key underpinning of HEKS/EPER's international work. HEKS/EPER supports, advises, promotes and accompanies Reformed Churches in Eastern Europe, Italy and the Near East in their socio-diaconal work and in building up vibrant church communities.
Many partner churches are located in Central and Eastern Europe. The largest group among them comprises the family of the Hungarian-speaking Reformed Churches in Hungary, Slovakia, Ukraine (Transcarpathia), Romania (Transylvania) and Serbia (Vojvodina). In the Czech Republic, HEKS/EPER works with the Evangelical Church of Czech Brethren and in Italy with the Waldensian Church. As of 2018, the CC mandate was broadened to include the Middle East, with Reformed partner organizations in Lebanon and Syria.