The Assessing adolescents’ psychological capital is a key step in designing preventive programs and promoting psychological well-being. Due to the lack of a culturally adapted instrument, this study aimed to develop and validate a tool to measure the psychological capital of Iranian adolescents based on the Covitality model (Furlong et al., 2014). This descriptive-survey research was conducted in two phases: instrument development and standardization. Initially, 408 items were generated, reduced to 180 after expert review, and a 120-item preliminary version was tested on 403 adolescents aged 12–18 in Tehran. Criterion validity was assessed using scales for emotion regulation (Garnefski & Kraaij, 2007), peer rejection (Tahmasian, 2005), self-efficacy (Muris, 2001), gratitude (McCullough et al., 2002), and empathy (Vossen et al., 2015). Data analysis using SPSS v.24 revealed four distinct blocks: Belief in Self (self-efficacy, self-awareness, and persistence), Belief in Others (support from school, peers, and family), Emotional Competence (emotion regulation, empathy, and self-control), and Engaged Living (gratitude, zest, and optimism). Internal consistency for factors and blocks ranged from 0.22 to 0.93, with correlations between blocks and the total scale ranging from 0.58 to 0.87. The total scale demonstrated high reliability, with a Cronbach’s alpha of 0.93, and criterion validity coefficients ranging from 0.25 to 0.55. The Adolescent Psychological Capital Scale demonstrated robust psychometric properties, confirming its validity and reliability for use in the Iranian adolescent population. This scale is suitable for educational, developmental, and research purposes, offering valuable insights into adolescents’ psychological capital and well-being. It can serve as a foundation for interventions aimed at fostering resilience and positive development among youth.