Community health worker (CHW) interventions to manage childhood illness is a strategy promoted by the global health community, which involves training and supporting CHW to assess, classify, and treat sick children at home. To inform CHW policy, the Government of Tanzania launched a program in 2011 to determine if community case management (CCM) of malaria, pneumonia, and diarrhea could be implemented by CHW in that country. This paper reports the results of an observational study on the CCM service delivery quality of a trial cohort of CHW in Tanzania, called WAJA. In the majority of cases, WAJA correctly assess sick children for CCM-treatable illnesses (malaria, pneumonia, and diarrhea) and general danger signs (90% and 89%, respectively), but too few correctly assess for physical danger signs (39%). In majority of cases (78%) WAJA treated children correctly (84% of malaria, 74% pneumonia, and 71% diarrhea cases). Errors were often associated with lapses in health systems support, mainly supervision and logistics. For CCM to be effective, in Tanzania, a strategy to implement it must be coordinated with efforts to strengthen local health systems.