SpaceOAR hydrogel, a novel biodegradable spacer, is increasingly used in managing prostate cancer patients undergoing radiation therapy to minimize rectal radiation dose and associated complications. However, its use has raised new concerns regarding its potential complications and impact on subsequent imaging interpretation. This article provides a pictorial review of the imaging complications of using SpaceOAR hydrogel in prostate cancer patients. We present multiple examples demonstrating the types of complications that can occur, potential underlying mechanisms, and their impact on patient outcomes and imaging interpretation. This review aims to provide radiologists and oncologists with an updated understanding of these complications, guiding better patient management and interpretation of imaging studies.