Today, marketers are starting to promote their CSR initiatives through the most popular SNS, such as Facebook and Twitter. However, little research has taken into consideration CSR campaigns promoted in SNS, and how consumers react to them. This conceptual paper submits the factors that influence consumer decisions to join a brand page in Facebook with a CSR oriented campaign: a) information of the company; b) personal concerns on the cause; c) image of the company; d) credibility of CSR initiatives; e) influence of peer-groups; f) self-brand congruity; g) perceived invasiveness; h) privacy concerns. All of these factors are expected to have a positive impact on consumer's attitudes toward the CSR campaign, except for perceived invasiveness and privacy concerns, which are anticipated to impact in a negative way.