Objectives: To investigate the existing model and mechanism for surveillance of the marketing of food for infants and young children in Phayao province, Thailand according to The Control of Marketing of Infants and Young Children Food Act, B.E. 2560 (2017). Method: This research was a qualitative research study which collected data through an in-depth interview and a focus group with 7 informants: officers of Phayao Provincial Public Health Office, registered nurses, public health technical officers, and consumer network officers. Results: Phayao province had a control model and mechanism on the marketing of food for infants and young children according to The Control of Marketing of Infants and Young Children Food Act, B.E. 2560 (2017) as follows: (1) For passive surveillance, there was a complaint center at the Provincial Public Health Office as the main coordinator to receive complaints and prepare files of violation cases. (2) Active surveillance included visits to target places such as shops and child development centers, and visits to enforce maternal and child health standards. Finally, (3) networking and knowledge dissemination were implemented through the first 1,000 miracle days of life project. The implementational model for controlling the marketing of food for infants and young children should be as follows: (1) Be compliant with laws. (2) Determine clear policies at the departmental levels. (3) Work collaboratively at the provincial, district, and subdistrict levels. (4) Increase participation of related people for surveillance of offences. (5) Empower operational networks, entrepreneurs, and other people to gain knowledge and be compliant with the law in a suitable way. (6) Use communication technology to support implementation. Conclusion: Phayao province has a model and mechanism to control the marketing of food for infants and young children in compliance with the law. The model and mechanism should be developed according to the area contexts to support the implementation to be more effective.