Background: Research in social cognition suggests that learning effectiveness in teacher-learner pairs may be influenced by how well their attention aligns with each other. However, we currently have limited understanding of how common distractions in real-world environments affect teacher-student interactions, specifically the synchronisation of their visual attention. Methods: This randomised controlled study investigates the impact of distractions on attentional synchronisation, learning performance, and cognitive load during training. A total of 29 medical students were randomly assigned to either a distraction group or a control group during a Transesophageal Echocardiography training in a simulation OR setting. Distractions were systematically induced in the experimental group, while attentional synchronisation was measured using a novel dual mobile eye-tracking technology. Results: The distraction group demonstrated lower attentional synchronisation, compared to the control group (Mean = 41.59% ± 6.89% [SD] vs. 50.96% ± 10.59%; Bonferroni-corrected t(27) = -2.84, p = 0.008, Cohen's d = 1.06). This reduction in attentional synchronisation was accompanied by significantly poorer practical and visual performances (d = 0.87 and 0.62), longer task completion times (d = 2.05), and higher intrinsic and extraneous cognitive loads (d = 1.09 and 1.04). Conclusions: These findings underscore the crucial role of attentional synchronisation in optimising work-based learning for complex clinical skills. Distractions in the learning environment disrupt the alignment of attention between teacher and learner, which impairs learning outcomes with substantial effect sizes. We outline several practical options to re-establish attentional synchronisation in distraction-rich learning environments.