Introduction: Lack of knowledge and proper feeding practices contribute to higher childhood morbidity and mortality. The aim of the study wasto evaluate the mother's knowledge and practices in terms of quantity, quality and timing of complementary feeding in infant and young child. Methods: A hospital based cross-sectional study was conducted between June, 2010 to October, 2011, at Kanti Children's Hospital, Nepal, involving 1100 mothers of children from 6 to 24 months of age who attended outpatient department of this hospital, applying systematic sampling technique using semi-structured questionnaire. Results: Eighty-seven percent of mothers had knowledge about the duration of exclusive breast feeding but only 33.0% practiced it and 21.0% breast fed their children up to 3 months. Eighty-seven percent of mothers knew when to start complementary feeding and 53.27% of mothers used the marketed weaning food. lito alone was offered by 28.27% as complementary food. Though 36.6% had proper knowledge of frequency of complementary feeding, only 33.27% were actually practicing it and 9.9% were offering more frequent thanrecommended. About half of the mothers fed their child with the food of appropriate consistency and 66.0% fed with the appropriate amount. But only 15.82% mothers fed their children with ideal frequency, sufficient amount and ideal quality. Conclusions: There was a knowledge and practice gap of duration of exclusive breast feeding and initiation and continuation of ideal complementary feeding. Rate of exclusive breast feeding was on declining trend.