Intertemporal decision-making requires weighing choice options that differ in timing and magnitude. In this context, individual preferences for immediate rewards despite lower payoffs are often interpreted as indicators of impulsive decision-making. While the dorsolateral prefrontal cortex (DLPFC) is known to play a role in decision-making, its specific function in intertemporal choices remains elusive. In our study, we investigated whether non-invasive stimulation of the left DLPFC reduces impulsive decisions. To this end, participants completed two sessions of a delay discounting task, in which they had to choose between fictitious smaller immediate and larger future rewards. In one session, anodal transcranial direct current stimulation (tDCS) was applied over their left DLPFC, while in the other session they received a sham stimulation. We fitted hyperbolic functions to each participant’s choice behaviour to quantify the individual degree of impulsive decision-making. Contrary to our hypothesis, stimulation of the left DLPFC did not reduce discounting of future rewards and thus not decrease impulsive decisions. However, tDCS-induced changes in affect were correlated with discounting rates, such that reductions in negative affect and increases in positive affect elicited by tDCS were associated with a decrease in impulsive choices under tDCS. Our findings suggest that stimulation of the left DLPFC does not exert a direct influence on intertemporal decision-making, but may affect decision-making indirectly through changes in affective processes.