Imran Okoth on Tuesday afternoon took oath in Parliament as Kibra MP after days of intensive campaigns and inter-party wrangles after his win.
Deputy President William Ruto and opposition leader Raila Odinga exchanged fiercely over Kibra by-election, with Ruto accusing ODM of instigating chaos.
But on Friday, President Uhuru Kenyatta approved the polls, arguing that the by-election was more peaceful than he expected, contradicting Dr Ruto.
“I saw the campaigns in Kibra and I was impressed because all my life Kibra was a no go zone. In Jubilee, we had a candidate and no one was hurt. People voted peacefully. A few people were stoned but no one was killed, no shop was looted… our candidate did not win but I have now believed that Kenya won,” Uhuru said during a meeting with leaders from Mt Kenya region in Sagana.
Mr Okoth will now take over formally from his late brother Ken Okoth, who succumbed to cancer in July this year. He had served as Constituency manager.
Fafi MP Abdikarim Osman on Tuesday ushered Imran to Parliament. He took oath at 2:36 pm East Africa Time.
He said in a tweet: "I welcomed Kibra MP-elect Hon. Imran @ImranOkoth to Parliament ahead of his taking of oath this afternoon. Karibu Ndugu."
Opposition leader Raila Odinga served as Kibra MP for twenty years before it was partitioned from the larger Lang'ata constituency.
Ken Okoth became the first MP of newly formed Kibra in 2013.
Kibra is the second-largest informal settlement in Africa after Soweto.