Ice-marginal lakes are an increasingly common feature of glacierised landscapes, and their sudden drainage beneath glaciers (a jökulhlaup) can threaten downstream communities and infrastructure. Numerous efforts to model jökulhlaups have been made, however, because these models are 1D representations of a single channel connected to a lake, they cannot simulate lateral jökulhlaup propagation through the subglacial system. Here, to simulate jökulhlaups within a 2D subglacial drainage system, we use a fully coupled model of subglacial hydrology and basal sliding with a time-evolving ice-marginal lake located at its boundary. In experiments on a synthetic domain, the model produces stable, recurrent jökulhlaup cycles, and glacier acceleration during flood onset followed by abrupt slowdown at peak flood discharge. Sensitivity testing highlights the efficiency of the subglacial hydrology system as a key control on flood timing, peak discharge, and the basal sliding response. We also explore our model’s ability to represent an observed record of jökulhlaups by applying it to Isunnguata Sermia, West Greenland. The model successfully reproduces variability over a 17-year period, but underpredicts peak flood discharges, likely because its formulation omits ice uplift and lake temperature variability. These results establish the coupling of a lake to 2D subglacial hydrology and ice dynamics as a viable approach for multi-decadal jökulhlaup simulation.