Empirical evidence suggests that habitat complexity is positively correlated to enhanced cognition across terrestrial and aquatic taxa. Coral reefs are one of the most spatially complex habitats on Earth, leading to the prediction that reef fishes would be cognitively advanced. However, coral reefs are degrading at an alarming rate following rapid environmental change. This change may have unforeseen effects on cognition in reef fishes, particularly given the well-documented neuroplasticity of teleosts. This study investigated the impact of habitat complexity on self-control in humbug damselfish (Dascyllus aruanus). Wild-caught juvenile damselfish were raised in high complexity (3D-printed corals) or low complexity (3D-printed coral rubble) environments for three months. Then, damselfish were tested in a detour-task by training fish to swim around a transparent barrier to receive a social and food reward. We expected individuals from high complexity environments to express higher inhibitory control than individuals from low complexity environments. Increased habitat complexity is associated with larger brains and telencephalons in fish, thereby augmenting advanced cognitive functions such as self-control. Understanding the effects of habitat complexity on reef fish cognition is crucial because cognition may be a key factor determining individual survival and species persistence in the face of rapid environmental change.