This paper explores how multi-agency response teams communicate and coordinate in different phases of a simulated terrorist incident. Procedural guidelines state that responders should coordinate their response to a major emergency across two phases: “response” (when the incident is ongoing) and “recovery” (when the threat has subsided, but the legacy of the incident is ongoing). However, no research has examined whether these phases map to the behaviours of responders in situ. To address this, we used measures of communication and coordination to examine how behaviours evolved during a simulated terrorist incident in the U.K. We grounded our approach within the theoretical literature on multi-team systems. It was found that the current response/recovery classification does not fit the nuanced context of an emergency. Instead, a three-phase structure of “response/resolve/recovery” is more reflective of behaviour. It was also found that coordination between agencies improved when communication networks became less centralised. This suggests that collaborative working in multi-team systems may be improved by adopting decentralised communication networks.