He is commemorated as a missionary on 7 November in the Calendar of Saints of the Lutheran Church with John Christian Frederick Heyer and Bartholomäus Ziegenbalg.

In the subsequent military expedition against Singamangaraja XII, known as the First Toba War, Nommensen played a prominent role in serving the colonial army as an interpreter and cultural consultant.

The area had greater Islamic influences, but Nommensen remained successful in building an indigenous Batak church.

Stephen Neill, in his History of Christian Missions, described Nommensen as "one of the most powerful missionaries of whom we have record anywhere" (page 348).

Another source wrote, "Nommensen may have been one of the most successful missionaries ever to preach the gospel" (Ambassadors for Christ, ed.