As many as 66 cases of bad nutrition at Yogyakarta Special Province trigger many problems in children’s growth and development. The role of nutrition is important in children’s growth and development. The role of feeding is very crucial for children’s growth and development; therefore they should be well-fed according to their needs. The objective of this research is to describe level of mothers’ knowledge about complementary feeding for babies at the POSYANDU of Modinan , Banyuraden, Gamping, Sleman, Yogyakarta. Research methodology: This research is a descriptive research using point time approach. The research took place at the POSYANDU of Modinan, Banyuraden, Gamping, SLeman, Yogyakarta from January – May 2016. The population consisted of 48 people. The sample consisted of 42 respondents using simple random sampling. The research variable is single variable using univariate analysis. Research result: Level of mothers’ knowledge about complementary feeding which is in good category is 59.5% or there are 25 people, moderate knowledge is 31.0% or there are 13 people, and low knowledge is 9.5% or 4 people. Conclusion: Level of mothers’ knowledge about complementary feeding at the POSYANDU of Modinan, Banyuraden, Gamping, Sleman, Yogyakarta is mostly in good category.