This study examined how the presence of economic support disclosure affects consumer attitudes toward influencer marketing from the persuasion knowledge model perspective. An experiment using the content of currently active YouTube influencers was conducted among 458 adults in the age range of ‘20-’30s. This study used a 2 (Presence vs. Absence of economic support disclosure) x 2 (Notebook computer vs. Beer advertisements) factorial design. The experiment started with a pre-test survey asking about attitudes toward influencers and brands. Four experimental groups were randomly assigned to stimuli and asked to complete a postexperimental survey measuring attitudes and the degree of persuasion knowledge activation. Results showed that the group without economic support disclosure presented higher persuasion knowledge activation than did the group with economic support disclosure. Further, the group with economic support disclosure exhibited a more positive attitude toward influencers than did the group without economic support disclosure. However, there were no differences between the groups with and without economic support disclosure in attitudes toward brands. The group with high persuasion knowledge activation level was more likely than the group with low persuasion knowledge action level to form a negative attitude toward influencers and brands. The current study posed that consumers would build attitudes by accumulating sufficient knowledge about advertisements (ads), filtering the ads, and perceiving the ads. This study contributed to offering a direction of influencer marketing and understanding influencer attitudes toward marketing.