The current study examined children's spontaneous private speech during the vertical and the horizontal Tube Task to shed light on the cognitive, motivational, and emotional processes underlying tool innovation. Tool innovation is defined as solving a novel problem by using or modifying objects in a new and useful way without prior instructions. Relations between private speech of 3- to 4-year-old children (N = 89) and their task performance (i.e., success and latency to success) were analyzed using Bayesian statistics. Children who were successful at the task produced more metacognitive and cognitive speech compared to children who were unsuccessful at the task. Latency to success did not relate to (meta)cognitive speech, but it was associated to negative speech: Children who expressed negative emotions more often and who evaluated the task as being difficult needed more time to find a solution than children who used less negative speech. These findings indicate that cognitive skills and emotion regulation are closely related in preschoolers' tool innovation.