Although knives are the most common homicide instrument in Britain, factors that influence knife-carrying tolerance (i.e., the extent to which it is seen as acceptable and justified) and perceptions of anti-knife messages (i.e., slogans and posters aimed at reducing knife crime) have not been examined, which the current article will cover by featuring progressively related studies. In Study 1, 227 men took part in a study on factors associated with knife-carrying. In Study 2, 200 participants took part in an experimental study on anti-knife slogans. In Study 3, 169 men took part in a study on existing anti-knife injury posters. In Study 4, 151 men took part in a study on anti-knife CGI posters featuring an avatar with different types of knife injury. Study 1 proposes a structural equation model that shows the intercorrelations between physical defense ability, limited trust in authority, limited control over one’s status and the need for respect, and how they predict aggressive masculinity (i.e., macho culture), which, in turn, predicts knife-carrying tolerance. The model also reveals two significant latent factors: saving face inter-male competition (i.e., honor) and perceived social ecological constraints (i.e., socioeconomic limitations). Study 2 shows that the injury slogan was rated as most persuasive. Study 3 shows that the fresh injury poster was rated as most persuasive, emotional, and believable. Study 4 shows that it was the eye injury that was rated as most persuasive, emotional, and believable. The article supports protection motivation theory and offers practical insights into tackling knife crime.