Using Kane's interpretive argument model and Messick's validity argument approach, this study rigorously examined faculty and PhD candidate’s perspectives on PhD admission interviews in Iranian universities. We interviewed 10 professors and PhD interviewees which provided comprehensive insight into nuanced perspectives. We conducted rigorous content analysis to identify prevalent themes, forming a strong foundation for our analysis. This study emphasizes the vital requirement for standardized evaluation criteria, robust support systems, and an enhanced interview process to ensure fair and inclusive admission systems. Additionally, our development of guidelines based on Toulmin's reasoning model underscores the originality of our contribution and its potential to benefit stakeholders and the Ministry of Science, Research, and Technology (MSRT) in Iran. The findings highlighted the importance of standardized criteria, support, and a stronger interview process for fairness and inclusivity in selecting PhD candidates. Faculty stressed clear guidelines to remove subjectivity, while candidates voiced concerns about unclear expectations and proposed added support like mentoring and preparation programs. Based on Toulmin's reasoning model, the study crafted validity argument guidelines for this context. As a result, these proposed changes will impact stakeholders and the MSRT by enhancing the PhD candidate evaluation process and ensuring a fairness and inclusivity. This study provides valuable insights to improve PhD admission procedures at Iranian universities by integrating standardized criteria, enhancing support mechanisms, and fostering fairness in decision-making.