BACKGROUND First branchial cleft anomalies (FBCAs) are rare congenital disorders with clinical manifestations and anatomy that are variable and complex. Due to the anatomical proximity to the facial nerve and association with infection, FBCAs require accurate diagnosis and careful management. The purpose of this report was to share the diagnosis and treatment of an extremely rare case of a 4-year-old girl with an FBCA presenting as a painless mass of the left external auditory canal and an inconspicuous depression in the left mandibular angle, a presentation that can easily be misdiagnosed as cholesteatoma of the middle ear. CASE REPORT A 4-year-old girl without any symptoms presented to our department due to "finding a mass in the left ear canal more than 2 months ago". Otoscopy, computed tomography, magnetic resonance imaging, and physical examinations supported the diagnosis of FBCA. The patient underwent surgery, which included resection of the first branchial fistula and canalplasty. Intraoperative findings revealed that the facial nerve straddles the fistula surface and that the fistula extends from the bottom oblique to the inferior wall of the external auditory canal. The postoperative diagnosis was "first branchial cleft fistula (Work type II)". No facial palsy or recurrence was noted during the follow-up period. CONCLUSIONS This report has highlighted the importance of the correct diagnosis and treatment of FBCAs and awareness of anatomical associations and complications. Careful otologic evaluation can help clinicians make a correct diagnosis. If preoperative examination reveals a connection between the superficial skin and external auditory canal, concurrent canalplasty should be performed.