In May 2022, Ellie Tang joined investment firm Fidelity International as director of sustainable investing, where she is tasked with integrating sustainability concerns into the company's real estate investments and help with formulating sustainability policies and product offerings. This shift came after six years with New World Development, where she was head of sustainability; until February 2022, she was also concurrently the general manager of sustainability at K11 Concepts. In these roles, she has fought climate change by turning the companies’ commitment to sustainability into concrete outcomes.

Since 2019, she has also been director of Nature Discovery Park, a biodiversity museum and sustainability-themed park located on the roof of the company’s K11 Musea development. She was previously a sustainability manager for property investment company Link REIT and before that for HSBC, where she made her name coordinating the HSBC Water Programme, a US$100 million public-private partnership to improve the supply of clean water. She is a member of the Hong Kong government’s Environmental Campaign Committee and Green Tech Fund Assessment Committee.