The anterior cingulate cortex (ACC), the basolateral amygdala (BLA), and the dopamine in the nucleus accumbens (NAc) are part of a neural system that is critically involved in making decisions on how much effort to invest for rewards. In the present study, we sought to identify functional interactions between ACC and NAc regulating effort-based decision making. Rats were tested in a T-maze cost-benefit task in which they could either choose to climb a barrier to obtain a large reward (LR) in one arm or a small reward in the other arm without a barrier. Experiment 1 revealed that bilateral excitotoxic lesions of the core subregion of the NAc impaired effort-based decision making, that is, reduced the preference for the high effort-LR option when having the choice to obtain a low reward with little effort. Experiment 2 showed that disconnection of the ACC and NAc core using an asymmetrical excitotoxic lesion procedure impaired effort-based decision making. The present data provide evidence that effort-based decision making is governed by an interconnected neural system that requires serial information transfer between ACC and NAc core.