This study investigates the direct and indirect impacts of extreme sea level (ESL) flooding on critical infrastructure. While methods to quantify the direct impacts of ESL flooding on coastal areas are well established, the indirect impacts that extend beyond the directly affected population are less well understood. This study assesses the vulnerability of electricity, road, telecommunication, water supply, and wastewater infrastructure to service disruption from coastal flooding in South Dunedin, New Zealand. We quantified the population affected by single and multiple service losses caused by 100-year average recurrence interval (ARI) ESL flooding across 0.1 m sea-level rise (SLR) increments up to 1.5 m. The study identified an ESL “tipping-point” at 0.6 m SLR, where direct loss of road access and electricity services is extensive, and causes indirect loss of telecommunication services. This also impacted the functionality of a key wastewater pumpstation servicing the wider region. As sea levels in the area are projected to rise 0.60 m in the next ~60–90 years, this information can inform assessments of potential adaptation investments in long-term infrastructure management plans in the face of uncertainty.