Islamophobia is the unfounded hostility against Muslims. While anti-Muslim feelings have been explored from many perspectives and in different settings, Internet-based Islamophobia remains under-researched. What are the characteristics of online Islamophobia? What are the differences (if any) between online and offline anti-Muslim narratives? This article seeks to answer these questions through a qualitative analysis of tweets written in the aftermath of the 2016 British referendum on European Union membership (also known as “Brexit”), which was followed by a surge of Islamophobic episodes. The analysis of the tweets suggests that online Islamophobia largely enhances offline anti-Islam discourses, involving narratives that frame Muslims as violent, backward, and unable to adapt to Western values. Islamophobic tweets also have some peculiar characteristics: they foster global networks, contain messages written by so-called “trolls” and “bots,” and contribute to the spreading of “fake news.” The article suggests that, in order to counteract online Islamophobia, it is important to take into account the networked connections among social media, news media platforms, and offline spaces.