The link between the physical self and markers of well-being and health behaviours has been demonstrated within existing literature (see Wilson, Mack, & Sabiston, 2011 for a review). Grounded in Basic Psychological Needs Theory (Deci & Ryan, 2002), the present investigation examined whether psychological need satisfaction served as one mechanism underpinning the relationship between moderate-to-vigorous physical activity (MVPA) and physical self-concept. Adopting a longitudinal design young adults (N= 147) completed questionnaires assessing MVPA, physical self-concept (PSDQ-PSC; Marsh, Richards, Johnson, Roche, & Tremayne, 1994) and perceived psychological need satisfaction in exercise contexts (PNSE; Wilson, Rogers, Rodgers, & Wild, 2006) on three occasions separated by three weeks. Serial mediation analyses with bootstrapped methods (Hayes, 2012) were adopted to test study objectives. Significant total (c1) and direct effects (c1’) of MVPA at Time 1 on PSDQ-PSC scores at Time 3 (β = .0050, t = 2.60, p = .01 and β = .0036, t = 2.26, p = .03 respectively) were noted. Examination of the specific indirect effects demonstrated that PNSE scores at each of the three time points mediated the MVPA Time 1 - PSDQ-PSC Time 3 relationship (a1a4a5b3 = .001; CI = .0001 to .0023). Contexts that afford individuals the opportunity to engage in exercise at a moderate-to-vigorous intensity, as well as, provide authentic and on-going support for psychological needs as identified by Deci and Ryan (2002), appear advantageous for the promotion of physical self-concept in young adults.