The objectives were to study and develop metacognitive skills of 1,616 early childhood in-service teachers in Child Development Center, Thailand. The quasi-experimental design were implied. Research Tools were Metacognitive Self-Assessment Questionnaire and scoring rubrics for early childhood students' assessment. Data were analyzed through fundamental statistics and inferential statistics. The research results were as follows: The teachers who joined with the program had got higher metacognitive skills score for both knowledge of cognition and knowledge of regulation than the other one. The teachers who had different supportive factors, different attitude towards pedagogy and different self-efficacy, would have got statistically significant difference in metacognitive skills in each dimension at the 0.01 level. Metacognitive skill score after participation in were higher than before in each dimension at the 0.01 level. Posttest score of early childhood students' metacognitive skills were statistically significant higher than pretest score in each dimension at the 0.01 level.