This study explored the influence of personality differences and their impact within coaching and mentoring relationships, through the use of the so-called Big Five personality traits: Openness, Conscientiousness, Extraversion, Agreeableness and Neuroticism. For analysis, surveys were conducted and semi-structured interviews were carried out with 100 participants from various industries. Using a mixed-methods approach, levels of data representation and analysis were evaluated using Pearson correlation and multiple regression for the purpose of validation. The research found statistically significant differences in relationships, with personality traits having a profound impact. Openness, Conscientiousness, Extraversion and Agreeableness had a positive correlation with effectiveness, while the trait Neuroticism had a negative impact. The compounded effect explained 68% variance in the effectiveness of coaching/mentoring. The findings provided insights into practice best-practices for added value in coaching and mentoring, with personalised approaches, effective communication, emotional support, trust building, flexibility and continuous feedback considered as key. The findings provide a comprehensive framework for understanding the relationship between understanding personality and their differences as a means to add value to coaching and mentoring prowess and improve outcomes in personal and professional terms.