The blackbody radiation shift of the Ga$^+$ $4s^2 ^1S^e_0 to 4s4p ^3P^o_0$ clock transition is computed to be $-$$0.0140 pm 0.0048$ Hz at 300 K. The small shift is consistent with the blackbody shifts of the clock transitions of other group III ions which are of a similar size. The polarizabilities of the Ga$^+$ $4s^2 ^1S^e_0$, $4s4p ^3P^o_0$, and $4s4p ^1P^o_1$ states were computed using the configuration interaction method with an underlying semi-empirical core potential. A byproduct of the analysis involved large scale calculations of the low lying spectrum and oscillator strengths of the Ga$^{2+}$ ion.