The EuII ion rivals GdIII in its ability to enhance contrast in magnetic resonance imaging. However, all reported EuII‐based complexes have been studied in vitro largely because the tendency of EuII to oxidize to EuIII has been viewed as a major obstacle to in vivo imaging. Herein, we present solid‐ and solution‐phase characterization of a EuII‐containing cryptate and the first in vivo use of EuII to provide contrast enhancement. The results indicate that between one and two water molecules are coordinated to the EuII core upon dissolution. We also demonstrate that EuII‐based contrast enhancement can be observed for hours in a mouse.