BACKGROUND: Triceps tendon avulsions (TTAs) are rare injuries previously reported in active young men or elderly adults. Little information exists when this injury pattern presents in younger patients. TTAs are at risk of being missed or misdiagnosed at initial presentation, leading to delays in treatment and recovery. We hypothesized that formally diagnosed TTAs in young patients can be detected early on plain radiographs using the avulsion fleck sign, leading to earlier diagnosis and treatment. METHODS: A retrospective case series of patients diagnosed with TTAs within the past 15 years at a tertiary pediatric referral center was reviewed. All patients were aged less than 21 years at diagnosis. Patient demographics, injury characteristics, clinical presentation, comorbidities, and radiographs were investigated to describe the presentation of TTAs in younger patients. Radiographs and advanced imaging were reviewed to assess for the avulsion fleck sign and examine if TTA diagnoses could have been made earlier if this sign was recognized. RESULTS: Nineteen patients met inclusion criteria, including 11 males and 8 females. The average age at the time of injury was 14.95 years (range: 12-19 years). 42.1% of subjects were injured during sports participation and 36.8% during play and daily activity. Only 2 patients had comorbidities. Initial radiographs occurred a median 0 days after injury (range: 0-14, interquartile range: 1). One of the 19 patients had their TTA diagnosed at initial presentation on a lateral radiograph. Eighteen patients had advanced imaging leading to diagnosis. Diagnosis was made a median of 7 days after injury, ranging from 0 to 520 days. One in 4 patients was diagnosed more than a month after injury. On retrospective radiographic review, 17 of 19 patients had the avulsion fleck sign detectable on initial radiographs. Advanced imaging characterized the avulsion and led to the diagnosis of associated imaging in 14 of 16 patients. CONCLUSIONS: There is limited information about TTAs in younger populations. TTAs present in both young females and males, and occur during sports participation, play, and daily activity. One in 4 patients had a delay in diagnosis more than 1 month from injury. Although advanced imagining was commonly used to diagnose TTAs, plain radiographs showed a consistent finding of an avulsion fleck sign. Accurate interpretation of plain radiographs can lead to a faster diagnosis of TTAs. Advanced imaging is indicated to fully assess the injury including associated pathologies.