ObjectiveThe aims of this study were to identify the unmet care needs and to examine the mediating effect of unmet supportive care needs in the relationship between functional status and quality of life (QOL) in Korean patients with amyotrophic lateral sclerosis (ALS).MethodThis was a cross-sectional study conducted among 186 patients with ALS recruited from a tertiary hospital in Seoul, South Korea. ALS patients' functional status, unmet supportive care needs, and QOL were assessed by Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised, the Amyotrophic Lateral Sclerosis Supportive Care Needs Instrument, and the Amyotrophic Lateral Sclerosis Specific Quality of Life – Revised Instrument, respectively. Mediation analysis was tested using Baron and Kenny's regression analysis and a Sobel test.ResultThe mean score for functional status was 33.35 ± 8.89; for unmet supportive care needs it was 2.40 ± 0.66; and for QOL it was 4.95 ± 1.29. Functional status was significantly correlated with unmet care needs and QOL. Unmet care needs satisfaction demonstrated a complete mediating effect on the relationship between functional status and QOL of the patients with ALS (β = –0.53, p < 0.001) and the effect was significant (Sobel test; Z = 5.48, p < 0.001).Significance of resultsAlthough QOL was negatively affected by the functional status in our sample, the relationship was fully mediated via unmet supportive care needs. Because there is no cure for ALS, and the condition is rapidly progressive with a lethal outcome, providing care by meeting patients’ needs is a critical aspect of caring for these patients. Early assessment of supportive care needs, providing services, and referring ALS patients to appropriate resources could enhance their QOL.