This paper is a natural continuation of the papers by Gavrilov and Gitman (
2000 Class. Quantum Grav, 17 L133, 2000 Int. J. Mod. Phys. A 15 4499) devot
ed to relativistic particle quantization. Here we generalize the problem, c
onsidering the quantization of a spinning particle in an arbitrary gravitat
ional background. The non-triviality of such a generalization is related to
the necessity of solving complicated ordering problems. Similar to the fla
t-spacetime case, we show in the course of the canonical quantization how a
consistent relativistic quantum mechanics of a spinning particle in gravit
ational and electromagnetic backgrounds can be constructed.