The present study investigated the effect of time pressure on 6th graders’ (11-12 years old) numerosity judgement strategies under three different time pressure conditions. Time pressure was manipulated by varying the maximum presentation time of the stimuli on three different levels: 5 s in the severe, 10 s in the moderate, and 20 s in the low time pressure condition. Analysis of the results in terms of the theoretical framework of Lemaire and Siegler (1995) revealed an effect of increasing time pressure on several parameters of strategy use such as participants’ strategy repertoire, relative frequency of strategy use and efficiency of strategy execution. Unexpectedly, we did not observe a significant decline in the adaptiveness of strategy choices as a function of item characteristics. Taken as a whole, these results indicate that children are already at a young age able to adapt their strategy use to the external demands of a task.