Objectives <p>Elevated maternal parenting stress not only contributes to adverse personal outcomes but also potentially hinders children’s development. Child-based worth, an emerging concept on which parents base their sense of personal value regarding their children’s performance, may constitute a risk factor for parenting stress, but its predictive role in parenting stress trajectories and underlying mechanisms remains understudied. This study examined how maternal child-based worth predicts parenting stress trajectories and the mediating roles of self-compassion and emotion dysregulation.</p> Method <p>A total of 724 mothers (<i>M</i>_age = 34.25, <i>SD</i>_age = 4.79) whose children were aged 7–12&#xa0;years (<i>M</i>_age = 9.87; <i>SD</i>_age = 0.72) completed follow-up questionnaires over 2 years. Latent growth and structural equation models tested trajectories and mediation.</p> Results <p>The results revealed that maternal parenting stress exhibited a declining trend over 2 years. Maternal child-based worth positively predicted the initial level of parenting stress (<i>β</i> = 0.20, <i>p</i> &lt; 0.001) but not the rate of change (<i>β</i> = −0.06, <i>p</i> = 0.37). After mediators were included, child-based worth predicted the initial level and rate of change in parenting stress solely through the mediating roles of self-compassion and emotion dysregulation.</p> Conclusions <p>Findings highlight the need for interventions that reduce maladaptive child-based worth cognitions and establish appropriate parenting expectations. Enhancing self-compassion while mitigating emotion dysregulation may represent promising targets for interventions to alleviate parenting stress stemming from maternal child-based worth.</p> <p>Preregistration</p> <p>This study is not preregistered.</p>