Post-mortem brain MRI can yield valuable information. However, tissue preservation and MR-compatibility of fixation agents are challenging. Here we investigated the effect of four MR-compatible formalin-based fixatives on the MR properties of pig brains at several timepoints after start of fixation up to one month. The inclusion agents known to improve the dielectric properties of the fixatives lead to greater R2* difference between GM-WM than conventional fixatives. Vice versa these agents lead to a decrease in T1 contrast.