China is facing challenges in both undernutrition and overnutrition, resulting from unhealthy diets. Nutrition education early in life, especially in school settings, has been reported to be effective in addressing these challenges. However, little is known about how nutrition education is delivered in schools in China. This study aimed to investigate the current status of delivering nutrition education by health teachers in Shanghai and to determine the barriers and resources that influence the teachers' practices and their willingness to teach nutrition. In 2016-2017, a cross-sectional questionnaire survey was conducted on 904 health teachers from 823 K-12 schools in Shanghai, China. There were 722 (79.9%) teachers that had the experience of teaching nutrition, but only 137 (19.0% of 722) spent ≥1 h teaching nutrition courses in each school year. Only 18.6% of the teachers had received a formal education in nutrition in college. About 88.5% of teachers expressed their willingness to teach nutrition in the future. The three major reasons for never teaching nutrition were categorized as: nutrition being taught by other teachers (39.5%), willing to teach but lack of knowledge (37.9%), and the subject not being required by school administrators (31.3%). Teachers who spent more time or were more willing to teach nutrition courses were those who were female, from private schools, had a better background in receiving nutrition education, and were more concerned about nutrition. Our data show that nutrition education is at a formative stage in Shanghai, China.