Objective: This study sought to examine the efficacy of inoculation message treatments to facilitate resistance to health nutrition-related (HNR) commercial food advertising claims. Design: Data were collected across three phases extending across a 5-week period conducted over two semesters at a Midwest US university. A 2 × 3 between-subjects factorial design was adopted, with multivariate and univariate analyses being used to interpret the results. Setting: Pittsburg, USA. Method: Participants were emerging adult undergraduate students (aged 18-25 years) recruited from introductory communication courses. A total of 167 students participated in Phase 1 of the work, of whom 152 completed Phase 2 and 145 completed Phase 3 (resulting in an 86.8% retention rate). Among these, 45% were men. Results: The results indicated (F(3, 129) = 9.83, p < 0.001, partial ?[superscript 2] = 0.18) that compared to control (M = 5.20, standard deviation [SD] = 0.84), participants who received an inoculation treatment experienced greater Phase 3 attitude strength (M = 5.73, SD = 0.77) to the position that eating healthy food is necessary to maintaining a healthy life. Inoculated participants reported greater Phase 3 attitude certainty (M = 77.15, SD = 19.21) for the above position than the control group (M = 65.43, SD = 25.48). Inoculated participants held less favourable views towards the source of the HNR claims (M = 4.80, SD = 1.18) relative to controls (M = 5.73, SD = 1.36) and generated greater numbers of counter-arguments (M = 3.90, SD = 1.74) compared to control groups (M = 2.75, SD = 1.69), thus demonstrating resistance to persuasion. Conclusion: Inoculation was demonstrated to be an effective preemptive strategy against potentially deceptive HNR advertising claims. Hence, it may offer an effective strategy for helping to protect the health conscious attitudes of emerging adults by providing resistance to the "pufferised" appeals used by many commercial food advertisers.