Metal tritide has been used for different areas such as research, purification, compression, and storage of tritium. Current radiation protection guidelines for tritium compounds describe the behavior of the metal tritide as the same as that of organically bound tritium. However, the biokinetic behavior of metal tritide varies according to materials. This study evaluated the behavior of zirconium tritide (ZrT) particles in rat lungs. The dissolution rate of the ZrT particles in simulated lung fluid was obtained from a specific setup. The ZrT was classified as type-S material according to its low dissolution rate. The ZrT particles were then instilled into rat lungs. The tritium retention time in different rat organs and tritium clearance from rats was obtained by sacrificing a total of 44 rats in a 6 mo period. A biokinetic model for ZrT particles in rat lungs was developed. The predicted retention curves with various phases of tritium in each organ agreed very well with the experimental data. The result can be used to estimate the human annual limit of intake and derived air concentration of ZrT particles.