The immediate former minister of environment, Amina Mohammed has resumed duty as the deputy secretary-general of the United Nations (UN).
Antonio Guterres, secretary-general of the UN, administered the oath her, at the UN headquarters in New York.
The ceremony was attended by the governors of Ogun and Borno state, Ibikunle Amosun and Kashim Shetimma.
Guterres appointed her in December.
She had served Ban Ki-moon, the immediate past UN secretary-general, as under-secretary-general and special adviser on post-2015 development planning.
Mohammed was instrumental in bringing about the 2030 agenda for sustainable development, including the sustainable development goals.
Before joining the UN, she worked for three successive administrations in Nigeria, serving as special adviser on millennium development goals.
She provided advice on issues including poverty, public sector reform and sustainable development, and coordinating poverty reduction interventions.
An adjunct professor in Development Practice at Columbia University, Mohammed has served on numerous international advisory boards and panels.
Speaking in Abuja during a valedictory service organised in her honour last week, Mohammed said the development of Nigeria and Africa, will be her priority at UN.
One of the notable projects that the ministry of environment embarked upon under her watch was the flagging off of the cleanup of Ogoni land.