Objective To investigate the clinical characteristics of patients with combined oxidative phosphorylation deficiency type 35(COXPD35) caused by TRIT1 gene mutations, in order to enhance clinicians' understanding of this disease. Methods A retrospective analysis was conducted on three patients diagnosed with COXPD35 resulting from compound heterozygous variants in the TRIT1 gene. Clinical data, auxiliary examinations results, genetic findings, and diagnostic courses were summarized and reviewed alongside relevant literature. Results All three patients were male children, with onset ages ranging from 5 months to 2 years and 3 months. They all presented initially with febrile seizures, which were later followed by myoclonic seizures and eventually progressed to refractory epilepsy. Common clinical features included microcephaly, intellectual disability, and pyramidal tract signs. Blood lactate levels were not significantly elevated. Genetic testing identified three TRIT1 mutation sites, among which c.172-2A>T and c.741G>A have not been previously reported in the literature. Conclusions COXPD35 caused by TRIT1 mutations typically begins with febrile seizures, followed by various seizure types, predominantly difficult-to-control myoclonic seizures. Patients may achieve normal developmental milestones during infancy, but experience psychomotor regression after seizure onset. Microcephaly and pyramidal tract signs are common, while lactate levels often remain normal.