Background: It has been assumed that prompting students to plan, monitor and evaluate their learning process could stimulate strategy use and thereby improve learning outcomes. Objectives: This study aimed to examine the effects of metacognitive prompts on students' self-regulated learning (SRL) and learning outcomes in the context of computer-based learning environments (CBLEs). Methods: To achieve this, the current study took a meta-analytic approach to critically evaluate evidence for the effectiveness of metacognitive prompts and identify potential moderators of the effects. Results and conclusions: With random-effects models, the results showed that metacognitive prompts significantly enhanced SRL activities (g = 0.50, 95% confidence interval [0.37, 0.63]) and learning outcomes (g = 0.40, 95% confidence interval [0.31, 0.49]) relative to the control conditions. Furthermore, moderator analyses revealed that the effects varied as a function of three prompts features: feedback, specificity and adaptability. Implications: Developing task-specific, individual-adaptive prompts and feedback should be a design principle in CBLEs, such that the prompt effect could be retained, sustainably enhanced and transferred to novel situations.