Aim Recent geriatric studies have focused on maximum voluntary tongue pressure against the palate (MTP) as a diagnostic value for dysphagia, as dysphagia causes aspiration pneumonia. Dysphagia can also cause water intake difficulties, resulting in hypernatremia by indicating the presence of hyperosmotic dehydration. However, no studies have reported on a possible association between reduced MTP and serum sodium levels. Methods To evaluate hyperosmotic dehydration within the normal range as an indicator of reduced MTP, we carried out a cross‐sectional study of 655 older Japanese community‐dwelling men (age ≥60 years) who undertook a general health check‐up from 2015 to 2016. As a high concentration of glucose influences serum osmolarity, which might act as a strong confounding factor on this association, the additional analysis was limited to individuals without diabetes. Reduced MTP is defined as a tongue pressure at or under the 20th percentile of the study population (≤24.0 kPa). Results Independent of classical cardiovascular risk factors, the adjusted odds ratio of reduced MTP for a 1‐standard deviation increment of serum sodium (2.21 mEq/L) was 1.29 (95% confidence interval 1.10–1.52). When the analysis was limited to individuals without diabetes, the association became slightly stronger, with an adjusted corresponding value of 1.59 (95% confidence interval 1.21–2.10). Conclusions Serum sodium level within the normal range is independently associated with reduced MTP in older Japanese men. This finding suggests that measuring the MTP is clinically relevant for estimating the pathophysiological values (such as dysphagia risks and aspiration pneumonia risks) in daily clinical practice. Geriatr Gerontol Int 2017; ••: ••–••.