We have measured saturation magnetization, ferromagnetic resonance linewidth, effective g factor, and magnetocrystalline anisotropy coefficients on single-crystal samples of praseodymium iron garnet (PrIG) and neodymium iron garnet (NdIG). Saturation magnetizations were measured from 77 to 550 K. The other properties were measured from 150 to 350 K in PrIG and from 200 to 450 K in NdIG. PrIG has a positive first-order magnetocrystalline anisotropy coefficient in contrast with all the other single rare-earth iron garnets. Our results support the idea that the contributions to linewidth and anisotropy of praseodymium and neodymium ions in an iron garnet lattice vary with lattice parameter.