Extra-dyadic relationships involve violation of relational trust and often lead to negative mental health consequences in young individuals. Despite the dominant norms around monogamy, Extra-dyadic engagements in pre-marital relationships of young individuals in India are a reality. While several studies have examined motivational factors for young individuals’ engagement in extra-dyadic relationships, the decision-making process related to the same remains under-researched. Using a qualitative approach, the present study delineates contributing factors for pre-marital extra-dyadic involvement of young individuals in India, explores emergent trajectories in the decision-making process, and highlights gendered trends related to this. Fourteen young adults (seven men and seven women) involved in extra-dyadic engagements were interviewed. For the analysis, the transcripts were grouped and coded using (Braun and Clarke in Qual Res Psychol 3:77–101, 2006) thematic analysis. Results showed that the first theme, “Why the unfaithful behavior?”, highlighted factors contributing to respondents’ decision to engage extra-dyadically. It was further divided into three subthemes, namely: relational troubles (trust issues, incompatibility, etc.); Intrapersonal factors (the need for experimentation and growth, etc.); and situational factors (use of alcohol, normalized extra-dyadic involvement, etc.). The second theme, “Impulsive versus thought-out decision,” is related to respondents’ decision-making trajectories concerning their engagement in extra-dyadic relationships. Three decision-making trajectories emerged, differentiating between impulsive and thought-out decisions. The trajectories revolved around relationship dissatisfaction, entry of alternative partners, fluctuating investment and commitment and disclosure and eventual resolution. The final theme highlights “Gender patterns,” such as the nature of engagement, relational outlook and how the contributing factors differed for men and women. The study presents implications for relationship education and counselling for conflict resolution and emotional regulation.