Police said they arrested George Aladwa at his home early on Saturday morning, before releasing him several hours later after questioning.
Aladwa is accused of helping to organise the January 30 symbolic swearing-in in Nairobi in front of tens of thousands of supporters, in a fresh challenge to President Uhuru Kenyatta’s re-election last year.
Police said Aladwa, who was arrested at his home on Saturday morning, was also being questioned over his role in a shooting Wednesday at the home of Odinga’s running-mate, Kalonzo Musyoka.
“Aladwa is being investigated over what happened at Kalonzo’s home. He is also being questioned over the chaos in (Nairobi) where he mobilised youths,” police spokesman Charles Owino told AFP.
Kenyatta’s victory in a re-run vote in October has sparked deadly clashes and polarised the country.
The government has denounced Odinga for trying to “overthrow” Kenyatta, while the opposition claims the election process was rigged and the result illegitimate.
At least 92 people have died in recent months, with most protesters killed at the hands of security forces, according to rights groups.
Aladwa’s detention follows the separate arrests this week of opposition firebrand Miguna Miguna and of lawyer TJ Kajwang for their alleged key roles in Odinga’s swearing-in.
The government also blocked three major TV channels to stop them from broadcasting the Tuesday’s “swearing-in”.
The stations remained off air Saturday despite a court order issued Thursday to end the suspensions.
Police have also ignored a judge’s ruling to release Miguna ahead of his court appearance scheduled for Monday.
“Tension is building up and it is just a matter of time before it explodes,” the Daily Nation newspaper wrote in an editorial Saturday.
“It is absurd that Mr Odinga and his coalition members have chosen the path of confrontation… but the government’s reaction is equally revolting,” according to the paper.
The United Nations and the US have denounced the Kenyan government’s crackdown.
But Odinga’s inauguration has also alienated him from the international community, with Western diplomats saying they were not in contact with him.
International calls for dialogue between the two sides have for months been ignored by both the government and opposition.