Based on message source theory, this study, under positive electronic word-of-mouth (eWOM) settings, examined the influence of message source credibility on brand attitude (brand trust, brand affection and purchase intention). And based on the elaboration likelihood model (ELM), the moderating effect of product involvement on the relationships between message source credibility and brand attitude were also examined. Data were collected via internet questionnaires. Based on the internet investigation, this study chose the stimuli of the research products, virtual brands and message source. Two hundred and eleven (211) effective samples were collected to verify the hypotheses of this study. The results, for both notebooks and shampoo, are as fol1ows: the positive eWOM message with higher message source credibility indicates a better brand attitudes than the eWOM message with lower message source credibility, and this effect is not moderated by the degree of product involvement, indicating its robustness.