Drawing on ability, motivation, opportunity (AMO) theory, this study seeks to contribute to the burgeoning scholarly discourse encompassing the instrumentality of green competencies (GCs) in catalyzing corporate sustainability performance (CSP). This study seeks to examine direct effect of GCs on CSP, the mediating effects of top management support (TMS) in the relationship between GCs and CSP, the moderating effect of green organizational culture (GOC), and finally the moderated mediation of GOC and TMS in causing GCs to affect CSP. To ascertain the associations among these constructs, three-wave time-lagged and multi-sourced data has been gathered from ISO-14001 certified Saudi firms. The empirical results confirm the hypothesized direct, mediating, moderating, and moderated mediation associations among the subject constructs. While concluding that a requisite accumulation (or cultivation/curation) of GCs, especially in green cultures, can impel top management to enthusiastically bolster green initiatives for superior sustainability performance. In addition, the authors suggest some mechanisms and boundary conditions through which GCs could be astutely deployed to boost CSP.