Nonradiative relaxation in Dy-doped fluoroindate glass is measured and characterized in terms of the well-known exponential energy gap law. It is found that although three low-lying Dy transitions fit well with an exponential dependence on an energy gap, the overall magnitude of the Dy decay rate is an order of magnitude higher than that of other rare earth ions. It is also found that the nonradiative decay rates in InF3 glass are comparable to those in ZrF4 glass, contrary to expectations based on maximum phonon energy. These unexpected results have important implications for a potential 4 μm Dy:InF3 fiber laser.