Flooding has become a recurring phenomenon in Port Harcourt Metropolis. Flooding poses significant threats to road transport infrastructure and the overall socio-economic development of the region. This study investigated the Impact of Flooding on Road Transport Infrastructure in Port Harcourt Metropolis. It identified flood hotspots, causes, and effects of flooding, the frequency and severity of flooding events, considers the effectiveness of current flood management strategies in preserving the road transport infrastructure and proposes mitigation strategies. The methodology involved using a simple random sampling design in a cross- sectional survey. A total of 385 questionnaire copies were distributed to gather data. In addition, field studies and personal interviews were conducted. The sample size of the study was 385 motorists that ply the various routes that were considered. Sources of data included primary and secondary sources. Analytical methods involved the use of tables, charts and cross-tabulations etc. Findings revealed critical flood hotspots in the Metropolis which are in three categories such as highly flooded areas, moderately flooded areas and lowly flooded areas. The highly flooded areas include the following: Nkpolu Road 1, Rumuigbo, Eneka Town, NTA/Apara Link Road, Rotimi Amaechi Drive, GRA, Phase 11, Kenka Road, off Mgbuoba Road, Abacha Road, GRA Phase 11, Orubo Close, Peter Odili Road, and BluePearl Street, Peter Odili Road. Areas captured under moderately flooded areas are Omachi Road, Rumuodomaya, Salem Close, off Ada George Road, Obi Wali Road, Rumuigbo, Diamond Valley Estate, Zion street, Rumuodomaya, Odani Road, Elelenwo, Evelyn Close, GRA Phase 11, Horsefall Street, Old GRA, and Alibaba Road, Old GRA, while the following are lowly flooded areas: Abanna Street, Old GRA, Hon Atta Close, Peter Odili Road, L.K. Anga Road, Peter Odili Road, Hilltop Road, Amadi Kalagbo, Uyo Street, Rumuomasi, Omerelu Street, GRA Phase 11, Akwaka Street, Rumuodomaya and Peter Odili Road. The study identified heavy rainfall, inadequate drainage systems, urbanization, poor physical planning and climate change as primary causes of flooding. These resulted in physical damage to road infrastructure, increased travel times, and economic losses. The research recommended infrastructure improvement, effective drainage systems, installation of flood forecasting and early warning systems, effective urban planning, and emergency response plans to mitigate the impact of flooding. These findings and recommendations provide valuable insights for policy makers, urban planners, and stakeholders to develop proactive strategies for flood risk management and for a sustainable transportation infrastructure development in Port Harcourt Metropolis.