Losses usually have greater subjective value (SV) than gains of equal nominal value but often cause a relative deterioration in effortful performance. Since losses and gains induce differing approach/avoidance behavioral tendencies, we explored whether incentive type interacted with approach/avoidance motor‐sets. Alpha‐ and beta‐band event‐related desynchronization (ERD) was hypothesized to be weakest when participants expected a loss and prepared an inhibitory motor‐set, and strongest when participants expected a gain and prepared an active motor‐set. It was also hypothesized that effort would modulate reward and motor‐set–related cortical activation patterns. Participants completed a cued Go/NoGo task while expecting a reward (+10p), avoiding a loss (−10p), or receiving no incentive (0p); and while expecting a NoGo cue with a probability of either .75 or .25. Pre‐movement alpha‐ and beta‐band EEG power was analyzed using the ERD method, and the SV of effort was evaluated using a cognitive effort discounting task. Gains incentivized faster RTs and stronger preparatory alpha band ERD compared to loss and no incentive conditions, while inhibitory motor‐sets resulted in significantly weaker alpha‐band ERD. However, there was no interaction between incentive and motor‐sets. Participants were more willing to expend effort in losses compared to gain trials, although the SV of effort was not associated with ERD patterns or RTs. Results suggest that incentive and approach/avoidance motor tendencies modulate cortical activations prior to a speeded RT movement independently, and are not associated with the economic value of effort. The present results favor attentional explanations of the effect of incentive modality on effort. This study investigates the effect of gains and losses on cognitive effort using pre‐movement event‐related desynchronization to measure attention and approach/avoidance motor tendencies. The results showed, for the first time, that approach/avoidance motor tendencies act independently of incentive modality, and that monetary gains contributed to improved effortful performance through increased attentional engagement.