Self-regulation--the monitoring and control of thoughts, feelings, and behavior--plays a central role in guiding healthy social development. While the bulk of the literature examining children's self-regulation has focused on how much or how well children can regulate specific cognitive functions or behaviors (e.g., emotion control, delay of gratification), recent adult research demonstrates the role of "metamotivation"--the monitoring and control of motivational states--in self-regulation. Metamotivation is guided by "metamotivational beliefs," including beliefs about which motivational state best fits the task at hand (beliefs about "task-motivation fit"). Research with adults demonstrates that having normatively accurate beliefs about task-motivation fit supports both individual achievement and social/occupational success. However, research has yet to investigate children's metamotivational beliefs. The current research addresses this gap by assessing children's beliefs about task-motivation fit. In Study 1, participants in middle childhood (N = 66; M[subscript age] = 7.7 years) rated how well they would expect to perform on "expansive-eager" tasks (tasks optimally performed with eagerness or expansion) and "contractive-vigilant" tasks (tasks optimally performed with vigilance or contraction) with eagerness (vs. vigilance) and expansion (vs. contraction). Study 2 was a direct replication of Study 1 with adult participants (N = 210; M[subscript age] = 39.3 years). Across both studies, participants had a general preference for vigilance over eagerness. While both children and adults reported some normatively accurate metamotivational beliefs about task-motivation fit, adults demonstrated these normatively accurate beliefs to a greater extent. These findings are discussed in terms of the importance of incorporating metamotivational beliefs into developmental models of self-regulation with the goal of supporting positive socialization and social developmental outcomes.