Mirid populations and their damages on cacao production have been widely studied in farms found under shaded conditions worldwide. The recent establishment of unshaded cacao plantations in Cameroon provided us the opportunity to assess the mirid abundance and damage in nine farms in three locations, from savannah to forest zones, in two consecutive years. Mirid abundance was assessed by visual counts of individuals and damage by scoring dry leaves on branches and cankers on twigs and trunks of trees. All mirids observed belonged to the species Sahlbergella singularis (Hemiptera Miridae). Generally, mirid numbers were low (0.26 ± mirid tree-1 for year 1 and 0.35 ± mirid tree-1 for year 2) and significantly lower in the Savannah zone (0.24 mirid cacao tree-1) than the transition zone (0.51 mirid cacao tree-1) and the forest zone (0.60 mirid cacao tree- 1). The Mirid damages was varied significantly (p<0.05) between plots, sites and years. However, damage due to cankers were very high (average median score: 1.20) compared to dry leaves ones (0.51). Our study showed a negative relationship between mirid abundance on cacao trees and the severity of their damages; this suggests that the observed damage are not only caused by the in situ mirid populations; but by a synergistic action of exogenous factors. These results contributed to a better understanding of the mirid ecology under unshaded conditions and should be taken into consideration when designing integrated pest management schemes against mirids.