Background: There has been much research on the average age at menarche onset. In higher income countries the lowering in average age at menarche is earlier than in middle-income countries and lower income countries. Indonesia as a middle-income country also has some research experience related to the average age at menarche for girls. Objectives: This study aimed to review the lowering of the average age at menarche in Indonesia and to predict changes in average age at menarche. Methods: This study provides a systematic review and meta-analysis using references from Google Scholar, PubMed and Popline databases on the trend of age at menarche in Indonesia and other data sources from local and national survey reports. Metaprop command in STATA was used to do the meta-analysis of proportion of early age at menarche and time series with auto-regressive integrated moving average (ARIMA) models were used in analyzing the trend and predicting the age at menarche. Results: The results show that in Indonesia the timing of age at menarche onset has significantly lowered during the 40 years before 2010. There was meaningful decrease of age at menarche, which changed from 14.43 years [confident interval (CI) 95%: 14.42, 14.44] to 13.63 years (CI95%: 13.63, 13.64). Using the ARIMA model, mean age at menarche onset for the next year predicted that the coefficient regression would be −0.0245 (CI95%: −0.0275, −0.0215). The predicted average age at menarche shows a decrease of 0.0245 years (8–9 days) each year. Conclusion: The findings indicate a significant lowering of age at menarche in Indonesian girls that has continued as a predictable trend through time until the present, paralleling recent socioeconomic changes. These predictions provide key indicators of a girl’s future healthy transition from childhood into young adulthood.