Purpose This study assessed the association between changes in sublingual microcirculation after a spontaneous breathing trial (SBT) and successful extubation. Materials and methods Sublingual microcirculation was assessed using an incident dark-field video microscope before and after each SBT and before extubation. Microcirculatory parameters before the SBT, at the end of the SBT, and before extubation were compared between the successful and failed extubation groups. Results Forty-seven patients were enrolled and analysed in this study (34 patients in the successful extubation group and 13 patients in the failed extubation group). At the end of the SBT, the weaning parameters did not differ between the two groups. However, the total small vessel density (21.2 [20.4–23.7] versus 24.9 [22.6–26.5] mm/mm2), perfused small vessel density (20.6 [18.5–21.8] versus 23.1 [20.9–25] mm/mm2), proportion of perfused small vessels (91 [87–96] versus 95 [93–98] %), and microvascular flow index (2.8 [2.7–2.9] versus 2.9 [2.9–3]) were significantly lower in the failed extubation group than in the successful extubation group. The weaning and microcirculatory parameters did not differ significantly between the two groups before the SBT. Conclusions More patients are required to investigate the difference between baseline microcirculation before a successful SBT and the change in microcirculation at the end of the SBT between the successful and failed extubation groups. Better sublingual microcirculatory parameters at the end of SBT and before extubation are associated with successful extubation.