Background The incidence and mortality rates of smoking-associated lung cancer are high among Chinese immigrant smokers. Coming from a country with different smoking policies, culture, and economic background than the U.S., Chinese smokers may change their smoking behaviors after immigrating to the U.S. Objectives This study aims to explore the trajectory of smoking behavior change among Chinese immigrant smokers migrating to the U.S. Methods This qualitative study was guided by the Grounded theory. Semi-structured intensive individual interviews were conducted among 10 eligible participants. A purposive theoretical sampling method was used to recruit participants through a website. Individual interviews were conducted online, via telephone, or in-person in Mandarin. Data were transcribed verbatim in Mandarin, translated into English, and triangulated with follow-up interviews and dialogues among authors to enhance trustworthiness and consistency of the study. Process coding and content analysis were used to analyze data. Results A total of 10 participants, 7 males and 3 females, were interviewed. Results showed the trajectory of smoking behavior change among Chinese immigrant smokers went through three phases: 1) Beginning to smoke, which included learning to smoke from others, trying to smoke and learning to smoke, and hiding their smoking behaviors from others; 2) maintaining smoking, which included setting boundary around smoking, smoking as a facilitator or barrier to social interaction, feeling pressures related to smoking behavior, and making others happy: Collective smoking and controlling smoking desire; and 3) changing smoking behaviors, which included experiencing life events that were triggers to changing smoking behavior, boredom as a reason for relapses, personal will as a key to quitting smoking, and quitting smoking for a loved one. Although some differences existed between male and female Chinese immigrant smokers' smoking behaviors, their trajectories of smoking behavior change were generally similar. Discussion Findings from this study can help health care providers to extend their understanding toward smoking behavior change among Chinese immigrant smokers across different socio-cultural contexts.