Multi-person decision making (MPDM) has numerous challenges for design decision making process during product development. The collaborative decision making process should be able to determine proper design attributes of a product, consider the relative importance of each attribute, and correctly combine all different perspectives of stakeholders to prioritize design alternatives in an unbiased way. Of all such challenges, the interpersonal trust factor can be critical since it directly affects decision making results and often obfuscates decision making. From this point of view, a multi-person design decision making method considering factors of social dynamics such as interpersonal trustworthiness and individual expertise is proposed in this research. Focusing on computational efficiency and simplicity, the whole decision making process, which ranks decision alternatives, is developed with a weighted scoring system. The weights on criteria are initialized through an interpersonal trustworthiness evaluation and updated through the Hopfield Network model. This updating system ensures that the more trusted stakeholders’ opinions have the higher influence on the final decision. The Trustworthiness Updating Decision Making Method is tested by a supplier selection example. The proposed method is posited to overcome the issues found in previous MPDM methods and to lead to more reliable solutions with less cognitive burden.