Introduction: Attachment anxiety and neuroticism were proposed to be associated with relative right frontal neural activity. Since sleep spindles are argued to reflect enhanced offline neuroplasticity, higher spindle activity measured over the right frontal areas relative to the corresponding left frontal ones could index higher attachment anxiety and neuroticism.Methods: 34 healthy subjects (male = 19; Mage = 31.64; SDage = 9.5) were enrolled in our preliminary study. Second night EEG/polysomnography records and questionnaire measures of personality (Zuckermann-Kuhlman Personality Questionnaire) and adult attachment (Relationship Scales Questionnaire) were collected. Frontal slow sleep spindles were measured by the Individual Adjustment Method (IAM), whereas hemispheric asymmetry indexes of spindle occurrence rate, duration and amplitude were derived as normalized left-right differences (electrode pairs: Fp1-Fp2, F3-F4 and F7-F8).Results: Relative right lateralization of frontolateral and frontopolar slow sleep spindle density and mid-frontal slow spindle duration were associated with attachment anxiety, but spindle lateralization was less closely related to neuroticism. The relationships between frontal slow spindle laterality and attachment anxiety remained statistically significant even after controlling for the effect of neuroticism. The attachment “relationship” dimension (need for close relationships) was related to relative left dominance of frontal slow spindle activation, whereas attachment independence was not correlated with frontal slow spindle lateralization.Conclusion: Right frontal lateralization of slow sleep spindle activity can potentially serve as a marker for attachment anxiety.