The understanding of consumers’ processes and activities that people engage in when searching for, selecting, purchasing, using, evaluating, and disposing of products and services to satisfy their needs and desires is crucial to guide marketers. Hence, the importance of the concept of source credibility in advertisement i.e. corporate credibility and endorser credibility. The aim of this study is to examine the effect of both the endorser and corporate credibility on consumer’s attitude toward ad, brand attitude and purchase intention when brand familiarity is tested. The model developed for this study is an integration of five separate “advertisement effect” models found in the advertising related literature. The study found that of the two source credibility investigated, endorser credibility portrays greater antecedent impact on Attitude toward advertisement than corporate credibility. The study also found that prior attitude toward brand is not a moderator for Attitude toward Advertisement and Attitude toward Brand. Attitude toward Brand is partial mediator for the relationship between attitude toward advertisement and purchase intention.