Background: Parental involvement is an important multi-faceted factor in children's academic performance and school behaviour. However, most prior studies have involved cross-sectional designs, with few studies exploring the co-developmental nature of various parental involvement characteristics over time and their associations with children's academic achievement, externalizing, and internalizing problems. Aims: This study explored (a) co-developmental trajectories of seven parental involvement characteristics in elementary schoolchildren, and (b) relations to children's academic achievement, externalizing, and internalizing problems. Sample and methods A total of 3553 Chinese elementary schoolchildren (M[subscript age] = 9.90, SD = 0.72; 53.9% boys) completed relevant measures on 4 occasions at 6-month intervals. Parallel process latent class growth modelling was used for examining study hypotheses. Results: Four co-developmental trajectories of parental involvement were identified: 'High motivation and involvement', 'Low motivation and involvement', 'Incongruent motivation and involvement', and 'Incongruent motivation and high involvement'. The highest academic achievement and fewest externalizing and internalizing problems were observed for schoolchildren in the 'High motivation and involvement' class, followed by those who were in the 'Incongruent motivation and high involvement' and 'Incongruent motivation and involvement' classes, and finally, schoolchildren were the 'Low motivation and involvement' class. Conclusions: The identification of heterogeneous trajectories with differential outcomes highlights the importance of individual differences considerations in understanding the co-developmental patterns of parental involvement, suggesting that specific interventions need to be formulated for differing groups.