Thyroid dysfunction after hematopoietic stem cell transplantation has been investigated in many studies. Most post-transplant thyroid disorders such as hypothyroidism are recognized as a late complication whilst hyperthyroidism is infrequent and transient, and usually happens early at the onset after transplant. Here, we report two rare hyperthyroid cases, developing more than 2 years after autologous stem cell transplant. We suggest that hyperthyroidism be alerted in the post-transplant care, and special attention be paid to any latent events.