We aimed to evaluate the relationship between insulin pharmacodynamics and glycaemic outcomes during closed-loop insulin delivery and sensor-augmented pump therapy. We retrospectively analysed data from a multicentre randomized control trial involving 32 adults with type 1 diabetes receiving day-and-night closed-loop insulin delivery and sensor-augmented pump therapy over 12 weeks. We estimated time-to-peak insulin action (t) and insulin sensitivity ($\_Ix\}$) during both interventions, and correlated these with demographic factors and glycaemic outcomes. During both interventions, t was positively correlated with pre- and post-intervention HbA1c (r = 0.50-0.52, P  < .01) and mean glucose (r = 0.45-0.62, P  < .05), and inversely correlated with time sensor glucose, which was in target range 3.9 to 10 mmol/L (r = -0.64 to -0.47, P  < .05). Increased body mass index was associated with higher t and lower S I (both P  < .05). During closed-loop insulin delivery, t, was positively correlated with glucose variability ( P  < .05). Faster insulin action is associated with improved glycaemic control during closed-loop insulin delivery and sensor-augmented pump therapy.