Background Completion total thyroidectomy with radioactive iodine (RAI) therapy is not uniformly recommended for minimally invasive follicular thyroid carcinomas (MI-FTCs) without distant metastasis, but may be considered for cases with a risk factor of recurrence, such as age ≥ 45 years. Objective The present study aimed to investigate the outcomes for patients with MI-FTC using a stratification age of 55 years. Methods The records of 478 patients with MI-FTC confirmed by surgical specimens at Ito Hospital from January 2005 to December 2014 were retrospectively reviewed. Twenty patients had distant metastasis at diagnosis and were subsequently classified as M1. Results Among the 478 patients with MI-FTC, univariate analysis identified that age ≥ 55 years ( p  = 0.002) and M1 ( p  < 0.001) were related to cause-specific survival. In 458 patients with M0 MI-FTC, male sex ( p  = 0.041), age ≥ 55 years ( p  = 0.001), and tumor size > 40 mm ( p  < 0.001) were related to poor disease-free survival (DFS) in univariate analysis. Multivariate analysis showed that age ≥ 55 years ( p  = 0.005) and tumor size > 40 mm ( p  = 0.005) were independent prognostic factors for DFS. The 10-year DFS rates of patients aged < 45 years, 45 years ≤ age < 55 years, and ≥ 55 years were 97.0%, 95.5%, and 86.4%, respectively. Conclusions The change in the recommended age for completion total thyroidectomy with RAI, from 45 to 55 years, seemed reasonable.