This study examined longitudinal associations of asthma management-related beliefs and behaviors with changes in asthma-relevant biological markers in a sample of 43 children with asthma. Children (M age = 12.4, 75% male) and parents were interviewed about asthma management beliefs and behaviors. Asthma outcomes included lung function (FEV1%), eosinophil counts, and daily cortisol measured at two time points, 18 months apart. Children with a less sophisticated disease belief (termed the “no symptoms, no asthma” belief) displayed eosinophil counts that increased over time, controlling for baseline levels. Poorer family asthma management was associated with increasing eosinophil counts over time. Poorer child asthma management was associated with cortisol output that declined over time. Further, families who reported poorer collaboration with their physician had children who displayed worsening lung function over time. These findings suggest that interventions aimed at teaching families better asthma management approaches and more accurate disease beliefs may have the potential to alter biological profiles in children with asthma.