Previous research has shown that gestures produced by caregivers and teachers facilitate children’s learning in problem-solving tasks. However, little is known about whether such facilitating effect varies with the task difficulty. We here asked twenty-eight three-year-old children to participate in two puzzle games (12-piece and 20-piece), with three episodes in each game. In Episodes 1 and 3, children played alone. In Episode 2, caregivers instructed their children (e.g., “Let’s put this piece upside down” while rotating left hand clockwise). For both puzzle games, children assembled more puzzles in Episode 3 than in Episode 1, suggesting that caregivers’ instructions were beneficial for children’s learning. However, such benefit was significantly greater in 12-piece than in 20-piece, t(27)=1.71, p<.05. This finding lends support to Vygotsky’s theory in which children can gain more from caregiver’s scaffolding when the task is within their capacity than when the task is beyond their capacity.