The 47-year-old joined the show in 1993 as an entertainment reporter but landed the top job of presenter three years later.
Phillips announced her decision to quit in August, citing family responsibilities as the primary reason. In a statement she said that leaving the breakfast programme was "the hardest decision I have ever made".
She later revealed that balancing the job with her home life had put a "real strain" on her marriage to the show's editor Martin Frizell.
"It's been a real strain. I can say it now that I'm going," she told Heat.
"He's the editor and there are things going on that he can't talk about. It's been difficult. Really difficult."
Sky News presenter Emma Crosby was recently unveiled as Phillips's replacement. The 31-year-old business reporter will take over in the New Year.