Maternal mental health remains a neglected component of maternal healthcare in many low- and middle-income countries (LMICs), despite the substantial burden of postpartum depression (PPD). In Nigeria, the integration of maternal mental health services into routine primary healthcare remains limited, resulting in delayed identification and inadequate support for affected women. This study explored postpartum mothers' experiences of maternal mental healthcare to identify service gaps and inform evidence-based strategies for improving maternal mental health services. A qualitative descriptive design was employed. Thirty-six postpartum mothers were purposively recruited from selected primary healthcare centres in Southeast Nigeria and participated in four focus group discussions. Data were audio-recorded, transcribed verbatim, and analysed using Braun and Clarke's thematic analysis framework. Three overarching themes emerged: healthcare neglect, characterised by limited recognition of mothers' emotional wellbeing during routine postnatal care; service gaps, including the absence of routine mental health screening, counselling services, and structured referral pathways; and desired support, reflecting participants' recommendations for empathetic provider communication, family-inclusive counselling, peer support groups, and improved community awareness. Participants consistently described stigma, inadequate psychosocial support, and limited access to appropriate mental health services as major barriers to care. The findings highlight significant gaps in maternal mental healthcare delivery within primary healthcare settings in Nigeria and underscore the need to integrate mental health into routine maternal services. Strengthening provider capacity, implementing routine screening, promoting family-centred care, and expanding community-based mental health support may improve access to timely and culturally responsive care. These findings provide context-specific evidence to inform maternal mental health policy and service delivery in Nigeria and other LMICs.