A complex dynamic systems perspective was applied to explore how mother and child mutually shape interpersonal coordination. Applying a microanalytic design, this study examined the moment-to-moment interaction behavior of 39 Dutch mothers and their three- and four-year-old children (53.8% girls, predominantly White) during a collaboration task. Fine-grained time-series data were extracted about the verbal, affective, and body movement modalities. "Research Findings:" Cross-recurrence quantification analysis showed that mothers and children were coupled within all three modalities. Recurrent behaviors were found with varying delays, spanning from the immediate to the entire length of the interaction. Many of the interactions were characterized by a certain degree of patternedness, whereby the amount of patternedness varied substantially between dyads. Measures of interpersonal coordination were not associated between modalities. "Practice or Policy:" Next to the content of interaction behavior (e.g., what a parent actually says), practitioners should also consider how behaviors of a mother and her child vary together. Thereby, an appraisal of the caregiver--child relationship should not merely focus on caregiving behavior, but acknowledge the active and autonomous involvement of the child. It remains to be investigated how different patterns of interpersonal coordination may serve as a diagnostic marker of (mal)adaptive child development.