A lot of confusion between UDL and DI exists, especially on how they exactly relate to each other. Consequently, a systematic review was conducted to identify all specific types of interrelationships between both pedagogical models in the literature. In total, 27 peer-reviewed articles were included. Three conceptual interpretations of the UDL and DI interrelationship were identified: 1) The complementary interrelationship between UDL and DI, which tended to diminish the status of either UDL or DI to an inferior category; 2) The embedded interrelationship of DI within UDL, which appeared as a consequence of interpreting DI as the act of differentiating; and 3) The incompatible interrelationship between UDL and DI, in which the studies tended to ignore most recent theoretical developments when contrasting both models. Our results clarify these different interpretations and present the assumptions that these are based on. Finally, we present future avenues of study towards empirical testing.