The singer passed the milestone over the weekend after his latest music video for festive track 'Mistletoe' reached 27 million views in a week.
To date, the star has amassed 2,004,247,332 views across the video-sharing site.
Bieber continues to hold the record for the most viewed music video on YouTube with his clip for 'Baby' currently sitting at 650 million hits.
Lady GaGa beat the 17-year-old to the 1 billion mark back in October 2010, but he quickly overtook and now has a lead of 320 million.
However, GaGa still remains the most popular person on Twitter with 15 million followers compared to Bieber's 13.9 million.
Meanwhile, Rihanna comes in as the third-highest YouTube star with 1.7 billion views and is currently the fastest-growing, while Eminem trails with 1.5bn.
> Eminem is 'most popular' on Facebook
The top 10 music stars on YouTube are as follows:
1. Justin Bieber - 2 billion
2. Lady GaGa - 1.88 billion
3. Rihanna - 1.7 billion
4. Eminem - 1.51 billion
5. Shakira - 1.21 billion
6. Black Eyed Peas - 1.11 billion
7. Britney Spears - 1.01 billion
8. Beyonce - 1 billion
9. Chris Brown - 868 million
10. Michael Jackson - 810 million
Watch the music video for Justin Bieber's 'Baby' below: