The study investigates the effect of Building Design Deficiencies on Post-Occupational Maintenance Costs in Public Buildings in Enugu Metropolis. The specific objectives of this study were to examine the effect of inadequate structural support (ISS) on Post-Occupational Maintenance Costs in Public Buildings and assess the effect of low integration of owner-occupier needs-expectations on Post-Occupational Maintenance Costs in Public Buildings in Enugu Metropolis. The study adopted a descriptive survey methodology. Data collection was facilitated using a structured questionnaire. The questionnaire included both yes-or-no questions and items measured on a 5-point Likert scale. The data were analyzed using SPSS 28.0. The result revealed that Inadequate structural support (ISS) has a significant positive effect on Post-Occupational Maintenance Costs in Public Buildings in Enugu Metropolis. And Low integration of owner-occupier needs-expectation has a significant positive effect on Post-Occupational Maintenance Costs in Public Buildings in Enugu Metropolis. The study concluded that reducing maintenance costs in Enugu’s public buildings requires a deliberate shift toward design-stage prevention: ensuring robust structural adequacy and embedding owner-occupier requirements into design decisions through systematic stakeholder engagement. The study recommended that Development control and procuring agencies should require full compliance with applicable structural codes, loading standards, and detailing requirements, particularly for public-use buildings with high occupancy and heavy usage.