Using a series of conventional large-scale household travel surveys conducted in the Osaka metropolitan area of Japan in 1980, 1990 and 2000 this study examines the mechanisms underlying children’s activity and travel engagements and how these mechanisms have changed over time. The results from a structural equation model show that, in the last two decades, children’s trip patterns in the Osaka metropolitan area have become more efficient through greater trip chaining. At the same time, the results also show that boys have become less mobile and their non-school activities tend to be in fewer locations than those of girls. Further, Japanese boys are the ones who travelled by car more frequently than girls. Denser built environments, accessibility by rail transport, and a higher number of school trips have constantly reduced the amount of children’s private car trips in the last three decades. Moreover, private car availability did not significantly increase the amount of children trip chaining in any observed year. This finding goes against the commonly held belief that public transport is less suitable for trip chaining. This is presumably due to the travel environment created by the well developed transit networks and dense land use in the study area.