Purpose: To reduce functional magnetic resonance imaging (fMRI) susceptibility distortion at the air/tissue interphase in animal experiments. Materials and Methods: We investigated the applicability of a body-adaptable flexible mold consisting of a fast-setting alginate. This technique was implemented for subcutaneous growing tumors in rats and for the brains of monkeys. Results: The T2*-weighted gradient-echo, echo-planar imaging (GE-EPI) data obtained with the body-adapted mold showed a reduction of susceptibility artifacts and improved image quality. With both rat tumor and monkey brain, an optimized match with the anatomical T1 images was possible. Conclusion: The present mold methodology is a rapid, easy, and inexpensive way to reduce magnetic susceptibility during animal GE-EPI.