Tongue-strengthening exercises (TSE) using a device have been proposed as an intervention for improving tongue strength and endurance. However, devices for TSE have been expensive and difficult to manipulate and are not commonly used in home or clinical settings. This study therefore aimed to investigate whether tongue-strengthening self-exercises (TSsE) using a tongue-strengthening self-exercise tool at home can improve tongue strength in healthy older adults. This study included 27 participants (exercise group, η = 16, 7 men, 9 women, median age 84.5 years; control group, n = 11, 2 men, 9 women, median age 79.0 years). Exercises in the exercise group consisted of pushing the anterior tongue against the hard palate 30 times, 3 times a day, 5 days a week, for 8 weeks using a tongue-strengthening self-exercise tool. This tool is available in five levels of hardness. The most suitable hardness of the tool for each participant was calculated based on 60% of maximum tongue pressure (MTP) during the first 2 weeks of the training period and 80% of MTP for the remainder of the training period, as assessed using a tongue pressure-measuring device. The exercise group showed a significant improvement of 4.1 kPa in MTP (an 11.53% increase) and 4.53 s in endurance of tongue pressure (ETP) (a 99.86% increase). Furthermore, adherence in the exercise group was 99.2%. In conclusion, performing TSsE for 8 weeks was effective for increasing MTP and ETP in healthy older adults. This indicates that TSsE may be useful in older individuals at home to prevent age-related tongue muscle weakness.