Purpose Late complications following implant-based breast reconstruction may raise concern for malignancy, including breast implant–associated anaplastic large cell lymphoma (BIA-ALCL). We report a case of a 71-year-old woman with prior bilateral mastectomy and implant-based reconstruction who presented with unilateral breast inflammation mimicking BIA-ALCL, ultimately diagnosed as bilateral implant infection with Corynebacterium amycolatum. Methodology The patient’s clinical course, investigations, operative findings, histopathology, microbiology, management, and outcomes were reviewed. Relevant literature regarding Corynebacterium species, implant-associated infection, and BIA-ALCL was examined. Results In late 2025, the patient developed progressive erythema, pain, and capsular thickening of the left breast refractory to antibiotics. Her history included an early postoperative infected seroma requiring washout and implant exchange. Imaging demonstrated peri-implant capsular thickening, a posterior soft tissue nodule, minimal effusion, and evolving axillary and internal mammary lymphadenopathy. Fine needle aspiration and flow cytometry showed reactive changes without malignancy. Following multidisciplinary discussion, bilateral explantation with capsulectomy and debridement was performed. The left capsule was thickened and erythematous, while the right appeared unremarkable. Histopathology showed chronic inflammation without lymphoma or carcinoma. Deep peri-prosthetic cultures from bilateral specimens grew Corynebacterium amycolatum. An extended course of intravenous vancomycin was completed following source control. Conclusion Corynebacterium amycolatum is an under-recognised implant-associated pathogen that may present years after reconstruction and closely mimic BIA-ALCL. This case underscores the importance of multidisciplinary assessment, explantation, and targeted antimicrobial therapy in atypical late implant presentations.