We tested whether decreasing respiratory frequency would stabilise both behavioural attention and pupil diameter oscillatory activity, compared to a spontaneously breathing control group. Pupil diameter was used as a proxy measure for Locus Coeruleus (LC) activity in order to directly test a prediction from a dynamical systems model (Melnychuk et al 2018) that posits the LC as a mediating nexus between respiration and attention. A novel task was designed, Paced Auditory Cue Entrainment (PACE) task, in which participants responded rhythmically to auditory cues, providing a continuous measure of sustained attention, and additionally, a breath guide for the experimental group. In Experiment 1, the respiratory frequency was guided from 0.15 Hz → 0.1 Hz → 0.15 Hz. In Experiment 2, participants spent a longer duration in each frequency, guided at 0.15 Hz → 0.1 Hz only. The two experiments yielded highly consistent results. Despite no group differences in the variation of the timing of responses, the control group committed significantly more lapses of attention in contrast to the breathing group, which barely committed any of such errors. Additionally, the oscillatory activity of pupil diameter in the breathing group closely tracked the frequency of the instructed breathing, implicating the possibility of LC-noradrenaline activity being entrained by the breath intervention. From these findings we conclude that decreasing respiratory frequency did indeed stabilise attention, mitigating lapses, possibly through stabilising fluctuations in LC activity.