Objective: Against medical advice, head and neck cancer (HNC) patients have been shown to continue to smoke and misuse alcohol post-diagnosis and treatment. This study aimed to better understand the barriers to and facilitators of health behavior change (HBC) in HNC patients. Method: We conducted nine focus groups following a standard protocol. Eligible patients were diagnosed less than three years previously with a primary HNC and selected using maximum variability sampling (gender, age, cancer stage, smoking, and alcohol misuse). Thematic analysis was conducted using NVivo 10 software. Results: Participants were mostly men (79%), 65 years of age (SD = 10.1), and married/common-law (52%, n = 15). Mean time from diagnosis was 19 months (SD = 12.3, range = 5.0-44.5), and most had advanced cancer (65.5%, n = 19). Participants provided a larger than anticipated definition of health behaviors, encompassing both traditional (smoking, drinking, diet, exercise, UV protection) and HNC-related (e.g., dental hygiene, skin care, speech exercises, using a PEG, gaining weight). The main emerging theme was patient engagement, that is, being proactive in rehabilitation, informed by the medical team, optimistic, flexible, and seeking support when needed. Patients were primarily motivated to stay proactive and engage in positive health behaviors in order to return to normal life and reclaim function, rather than to prevent a cancer recurrence. Barriers to patient engagement included emotional aspects (e.g., anxiety, depression, trauma, demoralization), symptoms (e.g., fatigue, pain), lack of information about HBC, and healthcare providers' authoritarian approach in counseling on HBC. We found some commonalities in barriers and facilitators according to behavior type (i.e., smoking/drinking/UV protection vs. diet/exercise). Significance of Results: This study underlines the key challenges in addressing health behaviors in head and neck oncology, including treatment-related functional impairments, symptom burden, and the disease's emotional toll. This delicate context requires health promotion strategies involving close rehabilitative support from a multidisciplinary team attentive to the many struggles of patients both during treatments and in the longer-term recovery period. Health promotion in HNC should be integrated into routine clinical care and target both traditional and HNC-related behaviors, emphasizing emotional and functional rehabilitation as key components.