The FRCSA strive towards unity in doctrine, worship and discipline with churches in South Africa and elsewhere in the world that exhibit the marks of a true church (as indicated in art. 29 of the Belgic Confession) not only on paper, but also in the everyday practice of church life. At local level there are currently promising negotiations in Pretoria between the FRCSA congregations Pretoria and Pretoria-Maranata, with the RCSA congregations Die Kandelaar, Totiusdal and Oos-Moot. In addition the FRCSA have good contacts with the Free Church of Southern Africa.
Internationally there are sister church relationships with:
- The Canadian and American Reformed Churches
- The Free Reformed Churches of Australia
- De Gereformeerde Kerken (vrijgemaakt) in The Netherlands (GKv)
From 2017 there was only a restricted sister-church relationship with the GKv (RCNL). Synod Belhar 2021 of the FRCSA decided the following about the relationship :
- That the RCNL, by the decisions of Synod Meppel 2017 regarding women in office as well as the trajectory of unification with the NGK, both of which were upheld by the Synod of Goes 2020, have deviated from the Word of God and undermined its authority.
- These decisions by RCNL synods are sufficient to terminate sister-church relations (in line with synod Soshanguve North 2017, art 44).
- Despite sufficient grounds as per points 1 and 2 above, for the sake of local churches and church members in the RCNL who have objections to the decisions of Meppel and Goes, to continue the restricted sister-church relationship as decided at Soshanguve-North 2017, art 44, 17.
- FRCSA synod 2024 will make a final decision, or will terminate the sister-church relationship if they unite with the NGK, whichever comes first.
- Although not included in the rules for sister-church relationships, the situation has forced synod to mandate Deputies to engage with concerned churches and members who object against the decisions of RCNL synods with the purpose of discussing the way forward.
The FRCSA is also a member of the International Conference of Reformed Churches (ICRC), bringing together several Reformed churches from around the world.