In today's digital age and with the surge of social media usage, influencer marketing has emerged as a popular tool for businesses to harness the power of social media in order to interact with their target market in a more credible and engaging manner. In using this tool, it is vital for businesses to carefully plan and select the right social media influencers for their brands. The notion of finding the right social media influencer prevail the need to understand the characteristics or traits of the social media influencer. Thus, this study aims to investigate how the social media influencer's traits specifically credibility, authenticity, and expertise can influence the consumer purchasing behavior for online products and be mediated by the trustworthiness aspect. The study is a quantitative research, whereby a simple random sampling will be used for participants' selection; the social media users who buy products using the TikTok platform. A self-administered online survey questionnaire with five-point Likert scale will be applied for data collecting purposes. Partial Least Square-Structural Equation Modelling (PLS-SEM) will be used to analyze questions on the SMIs traits: credibility, authenticity, and expertise on the consumer purchase behavior. This paper explores the traits or characteristics of social media influencers as well as the mediating role of trustworthiness in shaping the consumer buying behaviour. The implications for marketers include a better understanding of how consumers engage with social media influencers on social media. Results from this study may postulate a theoretical framework for measuring consumer buying behavior based on social media influencer traits.