The developmental origins of fear and its variations in individuals are poorly understood. Evidence suggests an attentional bias towards fearful faces emerges around 5-7 months of age. Our prior findings in 8-month-old infants indicate that neonatal left amygdala volumes were positively associated with attention disengagement probability from fearful faces. To our knowledge, this is the first study exploring the underlying white matter tracts. We used neonatal diffusion tensor imaging (DTI) data and eye tracking using an overlap paradigm with faces and non-faces as a behavioural measure collected in the FinnBrain Birth Cohort study (N = 86, 41 females). We used a whole-brain voxel-wise analysis that considered sex, age at the scan, age at eye-tracking, and maternal body mass index (BMI). We found that at 8 months, higher neonatal mean diffusivity was associated with lower chances of disengaging attention from fearful and happy faces. The results remained even after further controlling for maternal depression, smoking, and selective serotonin reuptake inhibitor use during pregnancy. According to sex-based stratification analyses, males in the sample drove the findings. The decreased integrity of the white matter tracts linked to fearful and happy processing in this infant sample raises the possibility that the sample's development is proceeding more slowly than that of other studies examining infants' emotional processing.Figure 1. Higher neonatal mean diffusivity was associated with lower attention disengagement probability from fearful and happy faces at 8 months (p = 0.05; 5000 permutations; multiple comparison corrections using threshold-free cluster enhancement). The colour bars represent 1-p.