The @UKAgainstISIL account will provide "updates on the UK government's ongoing work to defeat Isil".
Four posts have been made since it was set up on Thursday, including a video explaining the role the UK is playing in the struggle to defeat the group.
The footage says Britain is "militarily removing territory from Isil" and "cutting off Isil finances".
Islamic State - which is also known as Isil - often uses social media to spread its views.
A US study earlier this year claimed there were at least 46,000 Twitter accounts operating on behalf of IS.
British forces have been carrying out airstrikes against IS militants in Iraq, but no action in Syria has been approved by MPs.
There is speculation that Prime Minister David Cameron will push for a vote to extend the UK's involvement when Parliament returns from its summer break.
The UK government has created a dedicated Twitter feed to counter the Islamic State (IS) group.