The well-known ventriloquist illusion arises when sounds are mislocalized towards a synchronous but spatially discrepant visual stimulus. Recently, a similar effect of touch on audition has been reported. The present study tested whether this audio-tactile ventriloquist effect depends on hand posture. Participants reported the perceived location of brief auditory stimuli that were presented from left (AL; -10°), right (AR; +10°), and center (AC; 0°) locations, either alone or with concurrent tactile stimuli to the fingertips situated at the left (TL; -22.5°) and right (TR; 22.5°) of the speaker array. Compared to unimodal presentations, auditory localization was biased toward the side of the concurrent tactile stimulus, i.e. for ALTR and ARTL the respective correct responses decreased in favor of responses to the contralateral side. This effect was reduced but still significant when participants adopted a crossed hands posture. Here a localization bias was present only for large audio-tactile discrepancies (ALTR and ARTL), where the respective correct responses decreased in favor of center responses, indicating a partial (incomplete) bias. These results substantiate recent evidence for the existence of an audio-tactile ventriloquism effect and extent these findings by demonstrating that this illusion operates in an external coordinate system. The finding that hand posture modulates the audio-tactile ventriloquist effect, moreover, demonstrates that this effect is not exclusively due to a response bias.