The effect of breastfeeding on IVIM and non-Gaussian diffusion MRI was investigated. ADC0 and sADC values significantly decreased (P < 0.001 and P < 0.001) while K values significantly increased (P < 0.05) post-breastfeeding. fIVIM values significantly increased after breastfeeding (P < 0.01). No significant difference was found in D* values. There was significant heterogeneity in ADC0 maps post-breastfeeding, both in retroareolar and segmental scores (P < 0.0001 and = 0.0001). IVIM and non-Gaussian diffusion parameters significantly changed between pre- and post-breastfeeding status, and care needs to be taken in interpreting DWI data in lactating breasts.