Inappropriate complementary feeding is one of the major causes of undernutrition among young children in Tanzania. Prevalence of newly developed World Health Organization complementary feeding indicators and their associated factors were determined among 2402 children aged 6-23 months in Tanzania using data from the 2010 Tanzania Demographic and Health Survey. The survey used a multistage cluster sample of 10 300 households from the eight geographical zones in the country. The prevalence of the introduction of soft, semi-solid or solid foods among infants aged 6-8 months was 92.3%. Of all the children aged 6-23 months, the prevalence of minimum dietary diversity, meal frequency and acceptable diet were 38.2%, 38.6% and 15.9%, respectively. Results from multivariate analyses indicated that the main risk factors for inappropriate complementary feeding practices in Tanzania include young child's age (6-11 months), lower level of paternal/maternal education, limited access to mass media, lack of post-natal check-ups, and poor economic status. Overall, complementary feeding practices in Tanzania, as measured by dietary diversity, meal frequency and acceptable diet, are not adequately met, and there is a need for interventions to improve the nutritional status of young children in Tanzania.