Objectives: Many non-communicable diseases (NCDs) are caused by physical inactivity. 71% of all deaths globally and nearly half of all deaths in Pakistan are caused by NCDs. Despite the severity of the issue, a little research has accessed young adults’ physical activity (PA) in Pakistan. Therefore, this study aimed to explore the antecedents (attitudes, subjective norms, perceived behavioural control (PBC), perceived barriers, perceived gender norms and intentions) of PA while adapting the Theory of Planned Behaviour among Pakistani adults. Design: In this cross-sectional study, 233 Pakistani adults (18+) were recruited through the Qualtrics, based on convenience sampling. Two independent sample t-tests and four hierarchical multiple regressions were conducted to explore the predictors effect on intentions and PA. Results: There was no significant gender difference in PA. Females had higher perceived barriers than males. Hierarchical multiple regression revealed subjective norms (beta = .51, p p p p ’ subjective norms, perceived barriers, intentions and PBC should be considered to improve females PA and subjective norms for males PA. All predictors explained 35% of variance in intentions and 15% of variance in PA in the whole sample. Conclusion: Extended TPB is a useful framework to express physical activity antecedents among Pakistani adults and can be utilized to develop PA interventions to improve public health and well-being.