This study investigates the evolution of reading comprehension abilities in Indonesian learners of the Chinese Heritage Language (CHL), by comparing their scores on the Chinese Proficiency Test, a test specifically designed for CHL learners. A total of 275 candidates, divided into early adolescent (M[subscript age] = 13.56), late adolescent (M[subscript age] = 15.78), and adult (M[subscript age] = 22.83) groups, were evaluated on four dimensions of reading comprehension: orthographic knowledge, vocabulary knowledge, syntactic awareness, and discourse comprehension. A detailed cross-sectional and longitudinal analysis of these four dimensions was conducted across the three groups. The results indicate that horizontally, the order of the four dimensions is orthographic knowledge > vocabulary knowledge > syntactic awareness > discourse comprehension, with significant differences observed in all dimensions. During adolescence, orthographic knowledge is significantly higher than vocabulary knowledge, while in adulthood, vocabulary knowledge is significantly higher than syntactic awareness, and syntactic awareness is significantly higher than discourse comprehension. Longitudinally, reading comprehension abilities appear to stall across adolescence in three dimensions (vocabulary knowledge, syntactic awareness, and discourse comprehension), with a decline in one dimension (orthographic knowledge) occurring in late adolescence. However, the adult group shows improvement in all four dimensions compared to the late adolescence group. Considering both longitudinal and cross-sectional results, the developmental order of reading skills in Indonesian CHL learners is orthographic knowledge, vocabulary knowledge, syntactic awareness, and discourse comprehension. The main developmental peak for orthographic knowledge to vocabulary knowledge occurs in adolescence, while the major developmental peak for vocabulary knowledge to syntactic awareness and for syntactic awareness to discourse comprehension occurs in adulthood. The results suggest that reading comprehension improves significantly upon reaching adulthood in Indonesian. By understanding the trajectory of reading comprehension abilities in Indonesian CHL learners, this study can provide effective suggestions for Indonesian CHL learners and educators, and may also serve as a reference for other heritage languages.