Studies describing the link between infant sleeping arrangements and postpartum maternal depressive symptoms have led to inconsistent findings. However, expectations regarding these sleeping arrangements were rarely taken into consideration. Furthermore, very few studies on pediatric sleep have included fathers. Therefore, the aims of this study were (1) to compare maternal and paternal attitudes regarding co-sleeping arrangements and (2) to explore the associations among sleeping arrangements, the discrepancy between expected and actual sleeping arrangements, and depressive symptoms, in mothers and fathers. General attitudes about co-sleeping, sleeping arrangements and the discrepancy between expected and actual sleeping arrangements were assessed using the Sleep Practices Questionnaire (SPQ) in 92 parents (41 couples and 10 parents who participated alone in the study) of 6-month-old infants. Parental depressive symptoms were measured with the Center for Epidemiologic Studies-Depression Scale (CES-D). Within the same couple, mothers were generally more supportive than fathers of a co-sleeping arrangement (p < 0.01). Multivariate linear mixed model analyses showed that both mothers’ and fathers’ depressive symptoms were significantly associated with a greater discrepancy between the expected and actual sleeping arrangement (small to moderate effect size) (p < 0.05) regardless of the actual sleeping arrangement. These findings shed new light on the conflicting results concerning the link between co-sleeping and parental depressive symptoms reported in the literature. Researchers and clinicians should consider not only actual sleeping arrangements, but also parents’ expectations.