Guiding hints and challenge can help scaffold learners to progress beyond what they would achieve independently. The interactive and adaptive capabilities of mobile devices allow educational applications (apps) to support learning through scaffolding designs. However, little research has tested the effects of scaffolding features in apps on young children's learning. Using a 3 × 2 between-subjects design, this study experimentally tests how three types of app feedback (nonverbal sounds, verbal encouragement, or scaffolded verbal hints) and two types of leveling (gradual vs. random-ordered challenge) influence 4-5-year-old children's learning of novel words (N = 240). Results showed that scaffolded feedback was especially useful when provided at the beginning of app play (p < 0.01), and scaffolded leveling through gradual increases in difficulty supported faster and more accurate responses than random order challenge (p < 0.001).