Financial delays can disrupt cash flow and hinder resource mobilization in high-rise building projects. This study aims to identify and rank financial delay factors and formulate mitigation strategies for the Jakarta Technopark office project, a green building development in Grogol, West Jakarta. A quantitative descriptive approach combining surveys and a case study was employed. The Relative Importance Index (RII) was used to rank 48 indicators across eight categories based on stakeholders’ perceptions using a 1–5 Likert scale. Data were collected through offline questionnaires from May to June 2026. Reliability testing and RII calculations used 63 responses, while validity testing used 65 responses with an r-table value of 0.244. All indicators were valid, and reliability coefficients exceeded 0.70. The highest-ranked factor was delay in payment installment disbursement (RII = 0.892), followed by payment schedules not aligning with the contract (RII = 0.884) and owner budget limitations (RII = 0.879). The findings indicate that financial delays primarily arise from administrative processes and owner fund availability rather than contractor performance. Mitigation strategies include detailed installment schedules, reserve funds, accelerated digital verification, cash flow planning, bridging funds, payment prioritization for labor and subcontractors, and early procurement of materials and equipment. This study contributes by applying RII specifically to financial delay factors in a high-rise green building project and linking dominant factors with practical mitigation strategies. The findings provide a practical reference for project owners and contractors in improving cash flow management.