In this paper, we investigate the performance of free space optical (FSO) communication systems over imprecise Malaga (M) turbulence induced fading channel, which is the generalized form of the Gamma-Gamma and K turbulence channels as well. In the analysis we first derive the probability distribution function and cumulative distribution function of the channel's fading coefficient in the presence of channel estimation error. Then, we obtain the exact closed-form expressions of average bit error rate (BER), outage probability (OP), and ergodic channel capacity to quantify the performance of the considered system. Additionally, to provide further insights about the system performance in high signal-to-noise ratio (SNR) regime, the asymptotic expressions of BER and OP are obtained. Furthermore, analytic results are successfully validated with Monte-Carlo simulations. The results show that the imprecise channel estimation has detrimental effects on the performance of FSO communication systems over M turbulence channels, e.g., an estimation error of 5% results in approximately 8 dB SNR loss for the BER value of 5 x 10(-2).