Motivational deficits characterized by an unwillingness to overcome effortful costs are a common feature of neuropsychiatric and neurological disorders that are insufficiently understood and treated. Dopamine (DA) signaling in the nucleus accumbens (NAc) facilitates goal-seeking, but how NAc DA release encodes motivationally-salient stimuli to influence effortful investment is not clear. Using fast-scan cyclic voltammetry (FSCV) in male and female mice, we find that NAc DA release diametrically responds to cues signaling increasing cost of reward, while DA release to the reward itself is unaffected by its cost. Because endocannabinoid (eCB) signaling facilitates goal-seeking and NAc DA release, we further investigated whether repeated augmentation of the eCB 2-arachidonoylglycerol (2-AG) with a low dose of a monoacylglycerol lipase (MAGL) inhibitor facilitates motivation and DA signaling without the development of tolerance. We find that chronic MAGL treatment stably facilitates goal-seeking and DA encodin...