We present results from a 244 ks NuSTAR observation of 3C 273 obtained during a cross-calibration campaign with the Chandra, INTEGRAL, Suzaku, Swift, and XMM-Newton observatories. We show that the spectrum, when fit with a power-law model using data from all observatories except INTEGRAL over the 178 keV band, leaves significant residuals in the NuSTAR data between 30 and 78 keV. The NuSTAR 378 keV spectrum is well described by an exponentially cutoff power law (${\rm{\Gamma }}