<p>Periodic oscillations are widespread in biological systems, from heartbeats to predator-prey cycles. However, although oscillatory systems often exhibit modular organisation, how cycles are generated and coordinated across modules remains unclear. Here, we tested how modular nest architecture affects short-term activity cycles in the acorn ant <i>Leptothorax acervorum</i>. Activity cycles were consistently initiated by spontaneous pacemakers in the inner parts of the nest and transmitted toward the outer regions by intermediate ‘transfer’ ants. Compared to single-chamber nests, modular (double-chamber) nests induced partial decoupling of activity between chambers, resulting in reduced colony-wide rhythmicity. However, increased movement speeds of transfer ants in double-chamber nests relative to single-chamber nests enhanced activity transmission, partly restoring coordination between chambers. As well as illustrating how modular structure shapes collective dynamics, our results shed light on how ant colonies solve a fundamental challenge facing many biological systems: maintaining coordination between physically-segregated units.</p>