South Korea is a signatory of the Paris Agreement and has announced its aim to achieve carbon neutrality by 2050. However, South Korea’s current policy trajectory is not compatible with maintaining a global temperature rise below 2 °C. Climate change has not been a dominant electoral issue in South Korea, with national concerns being prioritized. A Paris-Agreement-compatible development pathway could synergistically improve ambient air quality in South Korea. This research examines the gains of a climate action pathway that would achieve 2050 carbon neutrality, compared to a business-as-usual (BAU) pathway, in South Korea. The work aims to add further evidence to the potential national gains from strong climate action across all sectors in South Korea. The paper argues that by focusing on and estimating national gains, the momentum for enhanced climate policy action can be intensified by framing robust climate action as an opportunity rather than a cost. Through a climate action pathway, South Korea could avoid 835 years of life lost (YLL) in 2030, 2237 YLL in 2040 and 3389 YLL in 2050. Through this pathway, South Korea could also cumulatively abate 5539 million tons of CO2 equivalent (MtCO2e) in greenhouse gas emissions over the 2022–2050 period.