Traditionally, acquisition of syntactic knowledge and the development of sentence comprehension behaviors have been treated as separate disciplines. This paper reviews a growing body of work on the development of incremental sentence comprehension mechanisms, and discusses how a better understanding of the developing parser can shed light on two linking problems that plague language acquisition research. The first linking problem is that children’s behavioral data that are observable to researchers do not provide a transparent window into the developing grammar, as children’s immature linguistic behaviors may reflect the immature parser. The second linking problem is that the input data that researchers investigate may not correspond veridically to the intake data that feed the language acquisition mechanisms, as the developing parser may misanalyze and incorrectly represent the input. Based on reviews of child language comprehension studies that shed light on these two linking problems, it is argued that further research is necessary to closely integrate parser development and acquisition of syntactic knowledge.