Background and Aims Postpartum psychiatric morbidities, including depression, anxiety, stress, and psychosis, pose significant risks to maternal and infant health, often leading to impaired bonding and long-term developmental issues. Despite global recognition, data from Indian tertiary care settings remain limited, particularly in southern urban contexts. This study aimed to estimate the prevalence of these morbidities among postpartum women and explore associations with sociodemographic and clinical profiles. Materials and Method A cross-sectional study was conducted at Kilpauk Medical College and Hospital, Chennai, involving 290 postpartum women aged ≥18 years, assessed 2–6 weeks post-delivery. Convenience sampling was used. After informed consent, sociodemographic and clinical data were collected via structured proforma. Validated tools included Mini International Neuropsychiatric Interview (MINI), Hamilton Anxiety Rating Scale (HAM-A), Edinburgh Postnatal Depression Scale (EPDS), Brief Psychiatric Rating Scale (BPRS), and Perceived Stress Scale (PSS). Data were analysed using SPSS version 25, with chi-square/Fisher's exact tests for associations (p<0.05 significant). Results Overall psychiatric morbidity was 35.17%, with depression (EPDS) at 13.10%, anxiety (DASS-21/HAM-A aligned) at 15.17%, stress (DASS-21/PSS) at 10.34%, and low psychosis rates. Depression was significantly associated with caesarean section (84.2% vs. 65.9%; p=0.024) and primiparity (73.7% vs. 56.3%; p=0.045). Anxiety (p=0.011) and stress (p=0.005) were higher among mothers of female infants. Conclusion Postpartum psychiatric morbidities affect over one-third of women in this tertiary cohort, driven by obstetric factors and cultural gender biases. Routine screening and multidisciplinary interventions are essential to mitigate risks and improve maternal-infant outcomes.