Introduction: Silent corticotroph pituitary neuroendocrine tumours (PitNETs) are rare, aggressive tumours that exhibit clinical and biochemical silence despite their expression of adrenocorticotrophic hormone (ACTH) and the transcription factor Tpit. They exist on a spectrum of functionality between true silent adenomas and ACTH-secreting adenomas and have been shown to rarely transform into functioning corticotroph adenomas. Case report: In this report, we describe an aggressive silent corticotroph PitNET, which recurred twice following complete excision and displayed functional transformation 128 months after primary excision, with clinical and biochemical profiles suggestive of Cushing’s disease. He underwent reoperation followed by hypofractionated stereotactic radiotherapy. Conclusions: This case report demonstrates the importance of long-term clinical and biochemical follow-up in patients with silent corticotroph PitNETs, as well as highlights the aggressive nature of these tumours that warrants early adjuvant radiation.