Unavoidable performance impairments occur when two tasks are completed simultaneously. These impairments, however, can be reduced with training. Research stemming from this has looked to investigate whether these training benefits can generalise (i.e., result in a corresponding increase in performance) to other untrained tasks via ‘training transfer’. In support of this notion, recent research utilising transcranial direct current stimulation (tDCS) has demonstrated a selective enhancement of training gains following online anodal stimulation on a single response-selection task. These modulated enhancements further transferred to an untrained visual search task, reflecting identical patterns of performance enhancement. Given these promising findings, this study aimed to extend on this research by investigating whether tDCS could selectively facilitate and modulate training gains on a dual response-selection task, and whether these effects could transfer to any of several untrained tasks (either related and unrelated to the task trained on) that utilise similar and distinct cognitive operations. Participants were trained on a speeded dual response-selection task which required manual responses to auditory and visual stimuli. Prior to and following training, participants also completed a control dual response-selection task, a visual search task, and a go/no-go task. Participant received either anodal, cathodal or sham online tDCS concurrent with training. Selective performance enhancements modulated by tDCS polarity were observed for both dual-tasks, suggesting that both training gains and modulating effects of tDCS transferred to an untrained task. The modulation effects of tDCS, however, slightly differed between the two tasks. Training transfer of training gains was also observed for the other untrained tasks, however, this was not affected by tDCS. These findings have broad implications in both professional, personal, and clinical settings in which enhanced responseselection provides a beneficial outcome – for example, in fast-paced job environments in which failure carries a high cost (e.g., national defines jobs), or in patients with schizophrenia, a disorder characterised by a deficit in response-selection processes.