Purpose: The purpose of this pilot study was to present basic data on shoulder musculoskeletal pain in junior elite tennis players, with data collected via a survey, physical examinations, and musculoskeletal ultrasound. Methods: The participants were eight healthy junior elite Korean tennis players, registered with the Korea Tennis Association. The participants’ characteristics were surveyed using a questionnaire, musculoskeletal pain was assessed, and physical examination and ultrasound examination of the shoulder were performed. Results: The average age of the participants was 13.1±0.8 years (range, 12–14 years), average duration of tennis experience was 3.5±1.5 years (range, 1–6 years), and average player career was 1.6±0.7 years (range, 1–3 years). Six players (75.0%) complained of shoulder pain during and after games. Tennis experience, career length, and training hours were not related to the during- or post-match musculoskeletal pain in the shoulder. Four players (50.0%) showed a 5° to 10° decrease (average, −7.5°±2.4°) in shoulder internal rotation. Acromioclavicular (AC) joint widening (average, 1.8±0.9 mm) was observed in the dominant shoulder in seven players (87.5%). Conclusion Decreased shoulder internal rotation was observed in half of the participants. Ultrasonographic evaluation confirmed significant AC joint widening in the dominant arm. Further research on AC joint widening in junior tennis players is required.