  We present results from a 244\,ks \textit{NuSTAR} observation of 3C\,273
obtained during a cross-calibration campaign with the \textit{Chandra},
\textit{INTEGRAL}, \textit{Suzaku}, \textit{Swift}, and \textit{XMM-Newton}
observatories. We show that the spectrum, when fit with a power-law model using
data from all observatories except \textit{INTEGRAL} over the 1--78\,keV band,
leaves significant residuals in the \textit{NuSTAR} data between 30--78\,keV.
The \nustar\ 3--78\,keV spectrum is well-described by an exponentially cutoff
power-law ($\Gamma = 1.646 \pm 0.006$, E$_\mathrm{cutoff} =
202_{-34}^{+51}$\,keV) with a weak reflection component from cold, dense
material. There is also evidence for a weak ($EW = 23 \pm 11$ eV) neutral iron
line. We interpret these features as arising from coronal emission plus
reflection off an accretion disk or distant material. Beyond 80\,keV
\textit{INTEGRAL} data show clear excess flux relative to an extrapolation of
the AGN model fit to \nustar. This high-energy power-law is consistent with the
presence of a beamed jet, which begins to dominate over emission from the inner
accretion flow at 30-40 keV. Modeling the jet locally (in the \textit{NuSTAR} +
\textit{INTEGRAL} band) as a power-law, we find the coronal component is fit by
$\Gamma_\mathrm{AGN} = 1.638 \pm 0.045$, $E_\mathrm{cutoff} = 47 \pm 15$\,keV,
and jet photon index by $\Gamma_\mathrm{jet} = 1.05 \pm 0.4$. We also consider
\textit{Fermi}/LAT observations of 3C\,273 and here the broad-band spectrum of
the jet can be described by a log-parabolic model, peaking at $\sim 2$\,MeV.
Finally, we investigate the spectral variability in the \textit{NuSTAR} band
and find an inverse correlation between flux and $\Gamma$.
