Background: Genomic sequencing technologies have identified isocitrate dehydrogenase (IDH) mutations in haematological malignancies. The prognostic implications of somatic IDH mutation (mIDH) in myelodysplastic syndromes (MDS) remain controversial. Methods: Mutations in IDH1 and IDH2 were detected using genomic sequencing technologies in 97 patients with MDS. Results: Seven (7.2%) mutations were identified: 3 in IDH1 (all R132C) and 4 in IDH2 (3 R140Q and 1 R140L). The frequency of mutation was 16.6% (2/12) in refractory anaemia with excess blasts (RAEB)-1 and 14.7% (5/34) in RAEB-2. IDH1/2 mutations were closely associated with higher bone marrow blast counts (median 10.0 vs. 2.3%; p = 0.019) and lower absolute neutrophil counts (median 0.44 × 109/L vs. 1.21 × 109/L; p = 0.027). All IDH mutations were mutually exclusive and heterozygous. IDH mutations were not significantly correlated with any specific karyotype. Patients with IDH1 mutations exhibited shorter overall and progression-free survival (OS and PFS; p = 0.039 and p = 0.042, respectively), whereas IDH2 mutations did not affect OS or PFS (p = 0.560 and p = 0.218, respectively). Multivariate analysis indicated that IDH1 mutation (p = 0.018; hazard ratio [HR] 4.735; 95% confidence interval [CI] 1.299-17.264), karyotype risk (p = 0.036; HR 1.619; 95% CI 1.033-2.539) and the revised International Prognostic Scoring System risk category (p < 0.0001; HR 2.122; 95% CI 1.401-3.213) were independent inferior prognostic factors. Conclusions:IDH1 mutation is associated with a poor prognosis.