We describe ultrasound-guided intralesional triamcinolone (ILT) injection for the management of chronic post-operative mammillary fistula (MF). Seven patients with chronic post-operative intraglandular MF were enrolled in this study. The initial response to treatment was assessed as complete in three cases; of the remaining four, three were resolved successfully with an additional ILT injection and the other had no resolution with an additional ILT injection. In five cases there was no recurrence after more than 1 year of follow-up. One patient had recurrence at 7 months, which was treated with a further ILT injection; this patient is without recurrence after a further 9 months' follow-up. This simple, safe procedure is suggested as an option for the treatment of chronic post-operative intraglandular MF and may be an alternative to surgery.