Abstract: Addressing the problem of increasing and diversifying sponsored eWOM on social media, this study examined the effects of different types of sponsorship arrangements and disclosure messages, with focus on (1) consumers’ perceived trust in the sponsored content creator and (2) attitudes toward the content creator and the sponsoring brand. An online experiment revealed interesting effects of sponsorship disclosure message types. High-detail sponsorship disclosure messages generated lower perceived benevolence only for search goods, and more positive attitude toward the reviewer only for experience goods. Different types of commercial gains disclosed do not seem to have systematic effects on consumers’ trust in the reviewer or attitudinal responses. However, some interesting patterns are found. The review disclosing the receipt of a free product seems to be perceived as equally acceptable as a review without disclosure and more effective than reviews disclosing general sponsorship, having received a payment, or having received a sales commission.