He started his career as a customs officer in 1958, two years before independence of Somalia. He rose through the ranks and became interpol liaison officer in Somalia and finally the country's chief police officer in charge of planning and training under the former regime of dictator Mohamed Siad Barre.
After law studies in Mogadishu National University and Fiscal Law School in Rome, he became attorney general, a post he held until 1991, when the country plunged into chaos, he had served as the Secretary General of the Somali Red Crescent Society (SRCS).
President Abdullahi Yusuf Ahmed nominated Hussein as Prime Minister on November 22, 2007, following the resignation of Ali Mohamed Gedi on October 29. Salim Aliyow Ibrow served as Interim Prime Minister between the tenure of Gedi and Hussein. Hussein was approved by parliament in Baidoa on November 24, receiving 211 out of 212 votes, and he was sworn in immediately afterwards. Hussein's government, which he described as "all-inclusive", was appointed on December 2, with 73 members; included in the government were 31 ministers, 11 state ministers and 31 assistant ministers. Hussein received some criticism for the exceptionally large size of the government; according to Hussein, in naming the government he followed the "4.5" formula required by the 2004 transitional charter, which provides for the division of posts between four main clans and a grouping of smaller clans. Four of the ministers—Hassan Mohamed Nur (who had been appointed Minister of Home Security), Abdikafi Hassan, Sheikh Aden Maden, and Ibrahim Mohamed Isaq—promptly resigned on December 3, complaining that their clan, the Rahanwein (one of the four major clans), was inadequately represented in the government and that they had not been consulted on their appointments beforehand. On December 4, Deputy Minister for Religious Affairs Sheikh Jama Haji Hussein also resigned, complaining of unfair allocation of posts in the government for his clan, the Jarerweyne, which is one of the smaller clans.
On December 17, Hussein said that he was replacing his previously appointed government with a "smaller, more effective administration". This new government was planned to include only 17 ministers and five deputy ministers, and was also to include people from outside of Parliament.
Hussein appointed 15 ministers and five assistant ministers on January 4 2008, and they were sworn in on January 5. Three additional ministers remained to be named. Parliament approved the new Cabinet on January 10, with 223 votes in favor, five opposing and two abstaining.
Since the Prime Minister came to office, he has pushed for continued peace and unity amongst the Somali nation. The peacekeeping truce which was signed in Djibouti in June 2008 was one of the outcomes of the work of Nur Adde and his government.
Hussein dismissed the Mayor of Mogadishu, Mohamed Omar Habeeb, on July 30; he accused Habeeb of incompetence, embezzlement, insubordination, and abuse of power. Habeeb, however, resisted this and said that his dismissal had to be approved by President Yusuf; he claimed to have Yusuf's support to remain in office. According to Hussein, his decision was supported by the people of Mogadishu and by the city's traditional elders. The issue of Habeeb's dismissal was believed to indicate deepening disagreement between Hussein and Yusuf.
10 ministers (including two deputy prime ministers) and one assistant minister resigned from Hussein's Cabinet on August 2 2008. The resigning ministers, most of whom were considered supporters of Yusuf, said that Hussein had not consulted them about Habeeb's dismissal; they also criticized Hussein for failing to present a budget to parliament. Hussein reacted by accusing the resigning ministers of trying "to create political instability in the country and disrupt the implementation of the Djibouti agreement between the Somali transitional government and the opposition", but he asserted that the government was still functioning properly. At the same time, referring to moves in parliament to impeach him, Hussein said that he was willing to resign if parliament dissolved the government or if doing so would benefit the peace process.
Hussein appointed six new ministers on August 3, saying that the remaining replacements would be appointed after consultations with the people. A no confidence motion against Hussein and his government was presented in Parliament on August 25. The motion alleged incompetence and embezzlement and criticized the government for failing to present a budget or provide national stability and security. It was submitted by 90 members of Parliament; Parliament had two days to review the motion. Hussein strongly denied the accusations of incompetence and embezzlement.
Hussein and President Yusuf signed a deal on August 26 that was intended to resolve the dispute between them, and they said before Parliament on August 28 that they had agreed on a number of changes, including the addition of five members to the Cabinet and the dissolution of the administrations in Mogadishu and Banadir Region. The vote of confidence against Hussein's government was held on September 1 and was overwhelmingly defeated; there were 191 votes in favor of the government, nine votes against it, and two abstentions.