CeIr3Ge7 is an antiferromagnetic metal with a remarkably low ordering temperature TN=0.63K, while most Ce-based magnets order between 2 and 15 K. Thermodynamic and transport properties as a function of magnetic field or pressure do not show signatures of Kondo correlations, interaction competition, or frustration, as had been observed in a few antiferromagnets with comparably low or lower TN. The averaged Weiss temperature measured below 10 K is comparable to TN, suggesting that the Ruderman-Kittel-Kasuya-Yosida exchange coupling is very weak in this material. The unusually low TN in CeIr3Ge7 can therefore be attributed to the large Ce-Ce bond length of about 5.7 Å, which is about 1.5 Å larger than in the most Ce-based intermetallic systems.