In this paper, we present a novel method to derive a tight upper bound on the symbol error probability (SEP) of a rotation coded scheme in the case of Rayleigh fading channels. This upper bound has a closed-form expression and provides results closer to the exact expression than the union-Chernoff bound. We present numerical simulations that show the tightness of the proposed analytical upper bound. Based on the tight upper bound, we also find the optimal rotation angle, which minimizes the derived tight upper bound expression of the SEP.