The bilateral axillo-breast approach (BABA) for robot-assisted thyroidectomy has some advantages over other minimally invasive thyroidectomies. However, some people do not consider this as a minimally invasive thyroidectomy because of the wider surgical skin flap. Thus, we devised mini-flap BABA robot-assisted thyroidectomy and analyzed the postoperative outcomes. The clinical records of 44 patients undergoing BABA robot-assisted thyroidectomy using a conventional flap or mini-flap were evaluated retrospectively. There were no significant group differences in clinicopathological characteristics. The operating and flap making times were shorter in the mini-flap group (206.18 ± 31.09 vs. 178.90 ± 34.43 min, p = 0.009; 38.85 ± 2.73 vs. 32.21 ± 8.62 min, p = 0.003, respectively). The total drainage amount was smaller in the mini-flap group (196.57 ± 81.40 vs. 150.74 ± 40.80 mL, p = 0.027). The numeric rating scale score and number of analgesics were lower at 2 h postoperatively in the mini-flap group (5.52 ± 0.87 vs. 4.57 ± 1.31, p = 0.006; 0.95 ± 0.22 vs. 0.65 ± 0.49, p = 0.012, respectively). There was no significant group difference in immediate oncological outcomes (p = 1.000). Mini-flap BABA robot-assisted thyroidectomy minimized the surgical flap and improved surgical outcomes. Therefore, it is a form of minimally invasive thyroidectomy. However, long-term follow-up of oncological outcomes is needed.