This study examined how sponsorship disclosure on television influences persuasion knowledge and brand responses (i.e., brand memory and brand attitude). Moreover, we tested whether extending disclosure duration increases its effect. By conducting an experiment (N = 116) we compared the effects of no disclosure to a 3-second and a 6-second disclosure. Results showed that especially a 6-second disclosure activates conceptual and consequently attitudinal persuasion knowledge. Regarding brand responses, we found that disclosure directly increased brand memory, regardless of duration. In addition, a 6-second disclosure indirectly resulted in less favorable brand attitudes through higher rates of attitudinal persuasion knowledge. Theoretically, this study provides insights into how sponsorship disclosure influences the persuasion process and the role of persuasion knowledge within this process.