This study aims to examine the differences between adult males’ and females’ friendships in terms of the primary and secondary capabilities that Positive Psychotherapy conceptualizes to reveal concrete realities in interpersonal relationships. The research is based on the convergent parallel pattern of a mixed methods research model. The correlational method is used in Study I, and the phenomenological design is used in Study II. In Study I, 1000 participants (536 females and 464 males) aged between 18 and 65 years, formed the sample. In Study II, 20 adults (10 females and 10 males) aged between 25 and 62 years are in the study group. For the analysis of the data, the SPSS-22 package program is used in Study I, and the MaxQDA Version 2018 computer program is used in Study II. The results indicate that in adult females’ relationships with their closest friends, the capabilities of love, patience, contact, trust, politeness, honesty, sincerity, justice, and reliability are statistically significant, and in adult males relationships with their closest friends, sexuality, achievement/diligence, thrift, and obedience are statistically significant.