The aim of this study was to compare the attachment styles and self-differentiation in parents with tendency to have one child and multiple children. This study had a causal-comparative (ex post facto) design. The research population was comprised of all parents of primary school students in Marvdasht city. Simple random sampling method was utilized and 50 parents with tendency to have one child and 50 parents with tendency to have multiple children were selected. The research instruments included Tendency to Have Children Questionnaire (Enayat & Parnian, 2013), Attachment Styles Questionnaire (Hazan & Shaver, 1987) and Self-Differentiation Scale (Drake, 2011). Multivariate analysis of variance (MANOVA) was utilized to analyze the data. The results showed that the mean scores of insecure attachment styles (anxious/avoidant and anxious/ambivalent) was higher in parents with tendency to have one child than parents with tendency to have multiple children, except for secure attachment styles which was higher in parents with tendency to have multiple children. Furthermore, findings indicated that parents with tendency to have one child had higher levels of emotional reactivity and emotional cut-off in comparison with parents with tendency to have multiple children except for I position.