The Starehe, Makadara and Juja by-elections followed successful petitions over irregularities during the 2007 elections.
The Starehe parliamentary seat fell vacant after the nullification of the election of Bishop Margaret Wanjiru by the High Court on July 30.
The election of Bishop Wanjiru, who also leads the Jesus Is Alive Ministries, was challenged by his main rival, former Sports minister Maina Kamanda.
The High Court ruled that Bishop Wanjiru, who was Housing assistant minister, was not validly elected.
Giving his verdict, Justice Kihara Kariuki said the poll was marred by massive tampering of election materials.
The judge said he did not know when and where the tampering occurred, but with the irregularities, Bishop Wanjiru was not validly elected.
Bishop Wanjiru became the seventh MP to lose her seat through an election petition, an indication of the flaws in the 2007 General Election.
It had been announced that the ODM lawmaker, had defeated Mr Kamanda of PNU by 895 votes.
Mr Kamanda disputed the outcome and filed a petition in February 2008. A vote recount was ordered and Mr Kamanda was found to have 49,306 votes against Bishop Wanjiru’s 34,871 — a difference of 14,435.
According to him, he lost the seat after Forms 16A were falsified.
But Bishop Wanjiru disputed his lead, saying the ballot boxes were interfered with at the Nyayo National Stadium, where they were kept after the elections.
In Makadara, Mr Reuben Ndolo of ODM disputed the election of Mr Dick Wathika of PNU.
Mr Wathika, former Public Works assistant minister, lost the Makadara seat in April.
Delivering judgment, Lady Justice Kalpana Rawal said the electoral process was marred by irregularities.
She said the election was not free and fair and that the returning officer abdicated her responsibility. Lady Justice Rawal said Mr Wathika was not validly elected.
Mr Ndolo served as Makadara MP prior to the 2007 elections.
In Juja, former chief whip George Thuo also lost his seat in April following a petition filed by Mr William Kabogo, a former area MP.
Nullifying the election, Mr Justice Luka Kimaru said Mr Thuo was not validly elected owing to massive irregularities by the disbanded Electoral Commission of Kenya.
The judge, however, absolved Mr Thuo of blame and directed the electoral agency to pay the costs of the suit by the petitioner, Mr Kabogo.
Recent by-elections saw Mr Omingo Magara of South Mugirango lose the seat to Mr Manson Nyamweya as Mr Joel Onyancha lost to Mr Simon Ogari in Bomachoge.
Mr Chirau Ali Mwakwere, who also lost an election petition, recaptured the Matuga seat in a by-election in July.
Several election petitions are still pending in court.