BACKGROUND: This study aimed to assess quality care behavior among nursing assistants and investigate potential influencing pathways based on the capability opportunity motivation-behavior (COM-B) model. Nursing assistants are the frontline staff responsible for most residents' daily care, and their care behaviors are closely associated with residents' quality of life. METHODS: A cross-sectional research methodology was implemented, and data were collected on demographic and sociological information, nursing assistants' quality care behaviors, care knowledge and skills, attitude toward older people, organizational climate, social support, work need satisfaction, and self-efficacy. The quality care behavior of nursing assistants was characterized using means and standard deviations. Key factors of quality care behavior were identified using structural equation modeling (SEM), ANOVA, Pearson's correlation, and the independent sample t-test. RESULTS: A total of 1,028 nursing assistants in 18 nursing homes in three central provinces were investigated. The mean total score for quality care behavior was 108.25 ± 12.33. The findings demonstrated that care knowledge and skills, attitudes toward older people, organizational climate, social support, and work need satisfaction directly and indirectly impacted quality care behavior. The cumulative effect of attitudes toward older people (β = 0.379, P <
0.001) and organizational climate (β = 0.295, P <
0.001) on quality care behavior was higher. CONCLUSION: Work need satisfaction and self-efficacy may have significant mediating effects in the link between capability (care knowledge and skills, attitude), opportunity (organization climate, social support) and quality care behavior. Facility managers should foster nursing assistants' professional identities by developing a supportive work environment that encourages their care practices.