Continuous flow has recently emerged as a powerful enabling technology that greatly improves many reactions’ efficiency. Here, we apply the technology to intermolecular [4+2] annulation of cyclobutylanilines with alkenes, alkynes, and diynes by photoredox catalysis. An across-the-board improvement in the annulation’s efficiency is noticed. Moreover, a gram-scale annulation is successfully demonstrated in continuous flow using a much lower catalyst loading. Continuous flow has recently emerged as a powerful enabling technology that substantially improves many reactions’ efficiency. Here, we apply the technology to intermolecular [4 + 2] annulation of cyclobutylanilines with alkenes, alkynes, and diynes by photoredox catalysis. An across-the- board improvement in the annulation’s efficiency is noticed. Moreover, a gram-scale annulation is successfully demonstrated in continuous flow using a much lower catalyst loading.