The striatum controls the execution of precise movements and action sequences. Whether to perform or not an action at the right time is key to survival. We have previously studied the activity of the dorsal striatum of adult rats (>p60) in a self-initiated task that required, after a minimum waiting time, the emission of an 8-licks sequence to obtain a reward. Interestingly, we found a modulation of the neuronal activity previous to the initiation of the learned sequence. This anticipatory activity was related to reward expectancy, reflecting the animals’ subjective valuation of timing. As regulatory circuits become mature during adolescence, we trained p30 rats in the same task with the aim of studying their striatal activity. Though adolescents were able to learn the action sequence and showed an improvement in the performance throughout training, they had a strong impulsivity prevalence: they made twice as much the number of premature entries with 8-lick sequences per reward as adults. Besides, they showed differential anticipatory activity between timely and premature trials, which also diverged from the neuronal activity of the adults. Together with the behavioral data, our results show age-related differences in the striatal signaling that could underlie the control of the timely execution of actions.