Fibroadenomas are the most common benign breast tumors in women. Giant juvenile fibroadenomas, which represent about 0.5% to 2% of all fibroadenomas, are a rare variant of these tumors. Giant juvenile fibroadenomas develop between the ages of 11 to 18 years and are usually unilateral and solitary. In the case presented, a 21-year-old woman was found to have multilobular fibroadenomas in both breasts, each with a maximum diameter of over 20 cm. The masses weighed 636 g on the right side and 752 g on the left. The patient underwent nipple-sparing mastectomy and immediate reconstruction with implant insertion in both breasts. This case is notable for the unusual size and shape of the masses, which presented considerable challenges for surgical removal and breast reconstruction. The patient was discharged without postoperative complications and remains under outpatient observation.