Abstract Compared to unenhanced nuclear magnets, e.g. Ag, Cu, AuIn 2, which undergo magnetic order at pK, nK, and μK temperatures, hyperfine enhanced nuclear magnets offer the possibility to study spontaneous nuclear magnetic ordering effects up to mK temperatures. However, the archetypal systems, PrNi 5 (T c =0.4 mK) and PrCu 6 (T c =2.7 mK) are restricted in their magnetic variety due to their clear tendency towards ferromagnetism. Here we present measurements of the dynamic susceptibility of the cubic Van Vleck paramagnet PrS at ultralow temperatures, 60 μK⩽T⩽100 mK , which give clear hints for an antiferromagnetic ordering transition of the hyperfine enhanced Pr nuclear moments at T N =90 μK . The nuclear fcc spin- 5 2 antiferromagnet PrS is a promising candidate for interesting spin structures.