The current study introduced a novel approach to inducing stress, and examining effects of wearable and mobile technology-assisted tactical breathing with real-time heartrate biofeedback, on the attenuation of acute stress, post-stressor recovery and performance. 39 participants with no prior experience with firearms participated in a marksmanship task engaging stationary targets with a semi-automatic rifle, at a controlled indoor shooting range. Novice shooters applying guided tactical breathing with biofeedback following exposure to the shooting task, were able to maintain lower arousal (uninhibited parasympathetic system). Findings suggested significant effect of intervention with biofeedback on stress attenuation, however no significant improvement of marksmanship performance among novice shooters resulting from the intervention was found. This study provides insights into app-led tactical breathing training to control arousal levels during stress, recommending strategies on further evaluation of the effectiveness of mobile and wearable technologies on stress attenuation for varying levels of marksmanship skill and individual difference.