While agile practices are widely adopted at the team level, extending agility to portfolio management remains a significant challenge, particularly in enabling continuous value realization within complex and volatile business environments. This paper investigates how agility and value delivery within an Information Systems (IS) portfolio can be enhanced by applying the principles of flow and the Theory of Constraints. Through an exploratory single-case study within an Indian fintech organization, we identify a cyclical framework for improvement encompassing flow visualization, constraint identification, constraint-aware resourcing, work-in-progress (WIP) limitations, accelerated learning, and dynamic reprioritization. Moreover, the study highlights foundational enablers like flow-optimized funding, metrics, and governance that collectively support agile portfolio capabilities. The findings indicate that applying flow principles and constraints management at the portfolio level helps to reveal bottlenecks, align resources strategically, enable rapid adaptation, and support system-wide optimization. The proposed conceptual framework advances the understanding of IS portfolio agility and offers actionable guidance for practitioners seeking to enhance the effectiveness and adaptability of portfolio management in dynamic enterprise contexts.