  Dc and ac-magnetic susceptibility ($\chi$), specific heat ($C_\mathrm{P}$),
electrical resistivity ($\rho$) and magnetoresistance measurements performed on
the new polycrystalline compound $\mathrm{Gd_2AgSi_3}$, crystallizing in the
$\alpha$-$\mathrm{ThSi_2}$ tetragonal structure, are reported. Two magnetic
phase transitions were observed in dc and ac susceptibility, specific heat, and
resistivity measurements at temperatures $\mathrm{T_{N_1}} = 11$ K and
$\rm{T_{N_2}} = 20$ K, despite a single site occupied by Gd atom, which is an
indication of the complex magnetic behavior. $\mathrm{Gd_2AgSi_3}$ turns out to
be one of the rare Gd compound in which a minimum is observed in the
temperature dependence of resistivity in the paramagnetic state and also
negative magnetoresistance over a wide temperature range (above
$\rm{T_{N_2}}$), mimicking the behavior of exotic $\mathrm{Gd_2PdSi_3}$, in
this ternary family. The isothermal magnetic entropy and adiabatic temperature
changes reach a value of 9.5 J/kg-K and 7.5 K respectively for the field change
of 9 T.
