  The Transiting Exoplanet Survey Satellite (TESS) continues to dramatically
increase the number of known transiting exoplanets, and is optimal for
monitoring bright stars amenable to radial velocity (RV) and atmospheric
follow-up observations. TOI-1386 is a solar-type (G5V) star that was detected
via TESS photometry to exhibit transit signatures in three sectors with a
period of 25.84 days. We conducted follow-up RV observations using Keck/HIRES
as part of the TESS-Keck Survey (TKS), collecting 64 RV measurements of
TOI-1386 with the HIRES spectrograph over 2.5 years. Our combined fit of the
TOI-1386 photometry and RV data confirm the planetary nature of the detected
TESS signal, and provide a mass and radius for planet b of $0.148\pm0.019$
$M_J$ and $0.540\pm0.017$ $R_J$, respectively, marking TOI-1386 b as a warm
sub-Saturn planet. Our RV data further reveal an additional outer companion,
TOI-1386 c, with an estimated orbital period of 227.6 days and a minimum mass
of $0.309\pm0.038$ $M_J$. The dynamical modeling of the system shows that the
measured system architecture is long-term stable, although there may be
substantial eccentricity oscillations of the inner planet due to the dynamical
influence of the outer planet.
