In her victory speech at the count in Camden, Abdi-Wali, who came to the UK as a child refugee from Somalia, said her victory was a testament to the success of diversity in the borough.
Later, speaking at a rally alongside Labour Party deputy leader Lucy Powell, she thanked voters for making her the MP “for this constituency that has given me so much”.
“It gave me a community, gave me a home, gave me an opportunity, gave me an education, gave me so many of my friends – everything I am today has been shaped by it.”
She told supporters that as an MP she would campaign on ending homelessness and taking Thames Water into public ownership.
Prime Minister Andy Burnham congratulated Abdi-Wali on a “fantastic campaign” while Burnham’s predecessor Sir Keir said she was “a brilliant champion for our communities”.
Asked what had gone wrong for his party, Polanski said the Greens had increased their vote share in the seat since the last election, describing the result as “our second best by-election result in Green Party history”.
“I’m not going to sit here and pretend I’m not disappointed. No politician runs in a by-election and doesn’t want to win,” he told BBC Radio 4’s Today.
“But at the same time, to see the growth in what was supposedly a safe Labour seat since 1983 [and] is now a marginal Labour seat, that’s clearly growth and next time we can get it over the line.”
Speaking to broadcasters earlier in the day, Polanski dismissed suggestions his leadership was under threat, saying: “Of course I can carry on as leader of the Green Party.”
He said voters had been “excited about our plans for rent controls, tackling the climate crisis and nationalising Thames Water”.