This study examined bidirectional relationship between mothers’ lax and overreactive discipline and children’s misbehaviour and negative effect. We examined the moment-to-moment stability of mothers’ and children’s behaviours (actor effects) and mothers’ and children’s influence on their partners’ subsequent behaviours (partner effects). Participants were 71 mothers and their 24- to 48-month-old children observed during a 30-min interaction. Both children and mothers exhibited stability in their own behaviours and influenced the subsequent behaviours of their partners. Additionally, a comparison of partner effects indicated that overreactive discipline more strongly predicted child’s negative effect than child’s negative effect predicted overreactive discipline. In contrast, although a child’s negative effect predicted lax discipline, lax discipline did not predict subsequent child’s negative effect.