This study examined the effect of brain hemisphere stimulation on effort intensity. We applied high-definition transcranial direct current stimulation (HD-tDCS) to the dorsolateral prefrontal cortex (dlPFC) to manipulate left or right hemispheric activity and assess its impact on cardiovascular responses reflecting effort. In total, 102 participants (65 women, 37 men) performed a mental concentration task under right cathodal, left cathodal, or sham stimulation conditions. We recorded cardiovascular responses, including pre-ejection period (PEP), systolic blood pressure (SBP), heart rate (HR), and diastolic blood pressure (DBP). Preregistered hypotheses predicted right cathodal stimulation to lead to greater left frontal hemispheric activity. This should result in higher effort during a mental concentration task of unclear difficulty by increasing approach motivation and thus success importance. As predicted, right cathodal stimulation increased PEP and SBP reactivity, indicating higher effort compared to the left cathodal and sham stimulation conditions. However, this effect was only evident in women, with men exhibiting a contrasting pattern. Our findings highlight the sex-specific effects of brain stimulation on cardiovascular responses reflecting effort, with the anticipated effects appearing in women.