Independent senator Lucy Gichuhi has defected to join the Liberal Party.
Prime Minister Malcolm Turnbull confirmed the news with Senator Gichuhi on his Twitter account with a video.
In the video, Mr Turnbull told Kenyan-born Senator Gichuhi: "Lucy, your life story is an inspiration - of enterprise and hard work, passion, freedom. And your values are so Liberal."
"Yes, I didn't discover that until I did my maiden speech and I thought, 'Wow - I can't believe how Liberal I am at the core'," she responded.
"And I think that really enables me to serve South Australians."
Mr Turnbull continued, asking: "You came to Australia because you believed this was the best country in the world to realise your dreams."
Senator Gichuhi responded with: "I did. And the fact that I could migrate here with my family was so important, and to be able to come here and be able to continue with that sense of freedom for the individual, that's really important for me.
"So all those - freedom, conscience, choice, religion - are really important to me."
Mr Turnbull said the South Australian senator embodied the Liberal values of freedom, enterprise, getting ahead and opportunity.
"Welcome to the Liberal family," the prime minister said as he ended the video.
Senator Gichuhi's switch is welcome news for the Coalition - boosting its voting numbers in the Senate to 30.
It restores the number of seats the Coalition had in the Upper House before the defection of Cory Bernardi.
But in most cases the Coalition will still need to secure an additional nine votes to pass legislation or eight votes to block motions.
Senator Gichuhi made history last year when she became the first person of black African descent to serve in the Australian Parliament.
She was born in a small Kenyan village and went on to study commerce at the University of Nairobi before relocating to Adelaide with her family in 1999.
Senator Gichuhi studied law and was working as a lawyer at the Women's Legal Service when an opportunity came to enter politics.
In 2016, Senator Gichuhi took an internship in Canberra with then-Family First senator Bob Day.
She ran as the only other name on the Family First ticket in the July 2016 election and when Mr Day resigned the following November, following a recount, she was elected.
In April last year, Family First merged with Cory Bernardi's Australian Conservatives and Senator Gichuhi chose to continue as an independent senator.
