This article describes the evaluation of a community-based participatory research (CBPR) community health worker (CHW) intervention to improve children's asthma-related health by reducing household environmental triggers for asthma. After randomization to an intervention or control group, 298 households in Detroit, Michigan, with a child, aged 7 to 11, with persistent asthma symptoms participated. The intervention was effective in increasing some of the measures of lung function (daily nadir Forced Expiratory Volume at one second [p = .03] and daily nadir Peak Flow [p = .02]), reducing the frequency of two symptoms ("cough that won't go away," "coughing with exercise"), reducing the proportion of children requiring unscheduled medical visits and reporting inadequate use of asthma controller medication, reducing caregiver report of depressive symptoms, reducing concentrations of dog allergen in the dust, and increasing some behaviors related to reducing indoor environmental triggers. The results suggest a CHW environmental intervention can improve children's asthma-related health, although the pathway for improvement is complex.