Curtain walls are a popular architectural element for the design of modern commercial building façade. With the advanced technologies and recent developments in building materials, curtain walls are developed with different lightweight materials, providing a spectacular visual identity of buildings and a number of functional design advantages to building interiors, including acoustic comfort, weather resistance, and thermal comfort. With the availability of high-performing glazed curtain walls these days, external noise in a commercial building adjacent to busy roads and railway lines is easily controlled, and acoustic comfort at internal space be achieved to suit the design intent. However, the lack of building design integration between building envelop, structural, and interior systems would often lead to airborne flanking noise transmission between different occupancies resulting in poor acoustic privacy. Such a post-design issue is often undesirable to the occupants and is an expensive exercise to retrofit. In this paper, a case study is conducted in a building where office workers in a three-story office building raised concerns about noise annoyance and acoustic privacy between two different tenancies on levels one above the other. This paper discusses the acoustic issues causing the compromised acoustic privacy, the method of acoustic investigations, the recommended noise control mechanisms, and finally the outcome of mitigation measures.