 Tight junctions, TJs, are essential for separating extracellular or luminal spaces from underlying tissues in epithelial and endothelial cell layers, and they maintain cell polarity through the regulation of occludin, a major family of integral membrane proteins. Occludin is regulated by phosphorylation, which plays a central role in TJ assembly and function. This article summarizes current knowledge on the kinases and phosphatases directly modifying occludin, and their roles in regulating TJ structure, function, and dynamics. This article was authored by Max Johannes Dorfel and Ottmahubber.