Introduction: Mitochondrial disorders are notorious for their wide phenotypic and genotypic heterogeneity with limited studies from India. This study aims at expanding the phenotypic-genotypic spectrum of mitochondrial disorders. Aim: To study the genetics of paediatric mitochondrial disorders by next generation sequencing (NGS) and to define the clinical and radiological phenotype of detected novel mitochondrial mutations. Methodology: Children were diagnosed with mitochondrial disorders based on Modified Bernier’s criteria 2002 (N=45). Results: Genetic study could be done in 15/45 children due to economic constraints.  The patients presented with wide range of clinical features namely neuroregression (N=5), spasticity (N=3),hypotonia (N=4),involuntary movements (N=5), ataxia (N=3),seizures (N=4),developmental delay (N=3), ophthalmological findings [ptosis (N=3), opthalmoplegia (N=3), optic atrophy (N=4),cataract (N=1)] sensorineural hearing loss (N=3), neuropathy(N=3) and elevated lactate (N=4). The children could be grouped into following clinical-imaging phenotypes: Leigh’s syndrome(N=3), Leigh/MELAS overlap(N=1), seizures with or without visual impairment and neuropathy (N=2), leukoencephalopathy (N=1), myopathy (N=1), spastic paraplegia (N=1). Genetic mutations (N=9,nuclear gene=8 and mitochondrial gene=1) and novel in eight.  The functional significance of the genetic mutations were complex I [N=1(MT-ND5-het)], complex IV [N=2 (SCO1,COX15-homo)],multiple complexes [N=1(NFU1-Homo)], translational machinery [N=2(PARS2,MRPS16-homo)], mitochondrial DNA rearrangement [N=2(POLG,C10ORF2-homo)] and vitamin metabolism [N=1(TPK1-homo)]. Parental study could be carried out only in one patient with COX15 mutation and the parents were heterozygous for this mutation. Conclusion: This study highlights the clinical and imaging characteristics in correlation with novel mutation in children with mitochondrial disorders from India. More number of similar studies will aid in targeted genetic analysis in paediatric mitochondrial disorders.