According to social media statistics service Famecount.com, Gaga recorded 5,635,460 followers earlier today, while Spears had 5,646,028.
With current growth rates, the "Bad Romance" singer should pass Spears' count on Thursday or Friday at the latest.
Spears' brief run at the top of Twitter began less than three months ago, when she overtook actor Ashton Kutcher for the top spot.
Famecount.com confirmed that Gaga's Twitter followers, 16 million Facebook friends and YouTube popularity currently make her the most popular entity online. However, the singer's Twitter crown is far from secure.
With Justin Bieber adding 800,000 new Twitter followers a month to his existing 4.5 million, the teen star could pass Gaga within six months.