Peritonitis- and catheter-related infections due to nontuberculous mycobacteria (NTM) including Mycobacterium abscessus have been reported among adults on peritoneal dialysis (PD). There is no recommended antimicrobial regimen for the treatment of M. abscessus peritonitis. Clofazimine has emerged as an important adjuvant antimicrobial treatment of M. abscessus lung infection. We report, to our knowledge, the first case of M. abscessus PD peritonitis in a child treated successfully using clofazimine as a novel adjuvant therapy to amikacin and clarithromycin. Her clinical features were similar to those of bacterial peritonitis, but she had persistence of symptoms and high inflammatory markers despite empirical therapy for peritonitis. Bacterial culture of PD effluent became positive for M. abscessus after 5 days. There was complete symptom resolution after 6 days of multidrug therapy. Due to ototoxicity, amikacin was discontinued after 6 weeks, while clarithromycin and clofazimine were continued for 9 months to ensure complete pathogen eradication before a planned renal transplant. A high index of suspicion in refractory or culture-negative cases is important for the diagnosis of NTM peritonitis. Multidrug therapy is recommended for M. abscessus infections. Clofazimine was chosen as a novel adjunct antimicrobial because of its pharmacokinetics, ease of administration, cost-effectiveness, and lack of serious adverse events.