In September, 2000, she was appointed by Secretary-GeneralKofi Annan, as executive- director of the United Nations Centre for Human Settlements. During her first two years in office, Tibaijuka oversaw major reforms which resulted in the United Nations General Assembly upgrading the Centre to programme status and renaming it the United Nations Human Settlements Programme. Tibaijuka was elected by the General Assembly to her first four-year term as head of the new agency in July, 2002 and was given the rank of under-secretary-general, as the first and only African woman to reach this level within the UN system.
In June 2005, the secretary general appointed Tibaijuka as his special envoy to study the impact of the Zimbabwean government's campaign to evict informal traders and people deemed to be squatting illegally in certain areas. As the evictions were concentrated on areas which had traditionally strongly supported the oppositional Movement for Democratic Change, many commentators believed the campaign was politically motivated. Although this was denied by the Zimbabwean government, there was strong international criticism. Tibaijuka concluded her report saying that “while purporting to target illegal dwellings and structures and to clamp down on alleged illicit activities, was carried out in an indiscriminate and unjustified manner, with indifference to human suffering”.
The steering committee of the Water Supply and Sanitation Collaborative Council elected Anna Tibaijuka as its new chair on 19 October 2010. Tibaijuka succeeded Roberto Lenton, whose second and final term of office ended in March 2011.
Blair Commission and Commission on Africa
In 2004 the British prime minister, Tony Blair, invited Tibaijuka to be a member of the Commission for Africa, which he established to generate ideas and action to accelerate and sustain Africa's growth and development. The Commission, comprising 16 internationally known figures, completed its report in March 2005.
Tegeta Escrow Scandal
In December 2014, President of the United Republic of Tanzania Dr. Jakaya Kikwete sacked Tibaijuka from a post of Minister for Lands, Housing and Human Settlement Development over her alleged involvement in the USD 250 million Tegeta escrow account scandal. Kikwete said he had asked Tibaijuka to “leave room for a new appointee,” after she had not shown "due diligence" when receiving USD 1 million from James Rugemalira of VIP Engineering and Marketing linked to the scandal. Tibaijuka had tried to defend herself that the money was a donation for the "Johansson Girls Education Trust" and that she had forwarded it after receiving it on a personal account.
Reelection 2015
In 2015 she was renominated by 63% of regional CCM members to run again for the parliamentary seat of Muleba South. She won the election and returned to the parliament.
Honours and awards
Awards
2009: Gothenburg Award for Sustainable Development
2016: Prince Khalifa Bin Salman Al-Khalifa UN Habitat Award for Sustainable Development