After his inauguration Madobe called on absent lawmakers to return to Somalia, in an apparent appeal to a group of MPs allied to the former speaker currently in neighbouring Djibouti.
Modobe is said to be a close ally of Abdullahi Yusuf, Somalia' interim president.
Rivals ousted
The removal of Adan's predecessor by Yusuf and Ali Mohamed Gedi, the prime minister, is widely seen as a punishment for his attempts to hold talks with the Islamic Courts Union which held power in Mogadishu, the Somali capital, until late December.
"Parliament has found a true leader who will lead it on the right way," Prime Minister Gedi told the house.
Yusuf also told parliament that he planned to hold a broad reconciliation conference of clan and religious leaders, saying he hoped it would take place within three weeks.
Some diplomats have criticised Adan's sacking, saying Yusuf's interim government had missed a chance to become more inclusive in a country divided along clan lines since warlords toppled a military dictator in 1991.
Hostility to Ethiopian soldiers
Supported by Ethiopian soldiers and weapons, the government drove out the Islamic courts who had held Mogadishu and other parts of southern Somalia for six months in a two-week war.
The United Nations security council urged the African Union on Friday to quickly send troops to Somalia to allow Ethiopia to withdraw its forces and the government to lift its emergency security measures.
Highlighting the continued threat of violence in the country, a policeman was shot dead in Mogadishu on Saturday.
The city has suffered a spate of attacks on Ethiopian and government positions, which some blame on supporters of the Islamic Courts Union, who had vowed to carry out a guerrilla war.