Ultrashort echo time magnetic resonance imaging (UTE-MRI) has been used to assess cortical bone porosity, as validated routinely with high resolution micro computed tomography (μCT). This study investigated the correlations between UTE-MRI-based quantifications and histomorphometric measures, as well as between UTE-MRI-based quantifications and μCT results. MRI properties showed strong correlations with both histomorphometric and μCT-based porosities. Only UTE-MRI could assess small pore (<40 μm) variations with moderate correlations. Major porosity changes were from large pores in studied specimens; therefore, μCT employment is likely adequate to validate UTE-MRI biomarkers. However, UTE-MRI techniques can assess pores below the detectable range by μCT, porosities which might contribute differently to bone mechanics.