When salient environmental stimuli occur repeatedly and in an expected pattern, mounting a fast and appropriate behavioral response is advantageous. For this, the brain needs to learn the pattern of the stimulus and predict the timing of the next stimulus onset. We investigated the neural basis of this process in larval zebrafish. We presented rhythmic visual stimuli to trigger swimming at defined inter-trial intervals (ITI) and simultaneously imaged activity in cerebellar Purkinje neurons (PNs). In randomly placed probe trials we omitted the visual stimulus. We found stimulus- and probe- driven activity in PNs. The probe-driven activity was acquired within three trials, was specific to the ITI duration and was adaptable to different ITIs. Interestingly, the stimulus-driven activity started to ramp up in anticipation of an upcoming stimulus, indicating that PNs predict the learned ITI. Robust probe-driven and predictive activity in PNs correlated well with faster behavioral responses. Occurrence of a probe trial increased response latency in the following trial, indicating reduced confidence in the learnt ITI. When the cerebellum was ablated, this probe trial-dependent behavioral plasticity was lost. All of these results indicate that PNs mediate the learning and updating of behaviorally relevant time intervals.