The management of recurrent head and neck adenoid cystic carcinoma (HNACC) remains a problematic challenge. This study aims to evaluate the long-term outcomes of personalized stereotactic ablative brachytherapy (SABT) as a salvage treatment for recurrent HNACC after surgery or external beam radiotherapy (EBRT). 21 patients with recurrent HNACC after surgery or EBRT successfully underwent iodine-125 (I-125) seed SABT from May 2011 to November 2019. The objective response rate (ORR), disease control rate (DCR), local control time (LCT), overall survival (OS), symptomatic relief and adverse events (AEs) were analyzed. Following SABT, the ORR and DCR were 85.7% and 100%, respectively. The 3-, and 5-year LCT rates were 68.8% and 55.1%, respectively, and the 3- and 5-year OS rates were 85.9% and 66.2%, respectively. Furthermore, univariate analyses showed that higher D90 (>137.1 Gy) was a strong positive prognostic factor of LCT (p < 0.05). The pain disappeared in one patient 3 months after SABT and partial pain improvement was observed in nine patients 1 to 6 months after SABT. Additionally, dyspnea was relieved in one patient with the tumor involving the trachea. The major AEs were mild intraoperative hemorrhage and skin/mucosal toxicities which were generally graded ≤2 and well-tolerated. Personalized SABT was an effective and safe alternative option for recurrent HNACC after the previous failure of surgery or EBRT. The parameter of D90 may influence the local control.