Sarcopenia, similar to hypercortisolism, is characterized by loss of muscle mass and strength. Cortisol circadian rhythm changes with aging (blunted late-day nadir values) were suggested to contribute to this decline. We aimed to explore the relationship between diurnal salivary cortisol values and sarcopenia diagnosis and its components in postmenopausal women. This is a cross-sectional study within the OsteoLaus population-based cohort in Lausanne (Switzerland). Participants had a body composition assessment by dual X-ray absorptiometry (DXA), a grip strength (GS) measure, and salivary cortisol measures (at awakening, 30 min thereafter, 11 AM (sc-11AM) and 8 PM (sc-8PM)). Associations between salivary cortisol and sarcopenia diagnosed by six different criteria (based on appendicular lean mass (ALM) assessed by DXA, and muscle strength by GS), and its components, were analyzed. 471 women aged > 50 years (63.0 ± 7.5) were included. Various definitions identified different participants as sarcopenic, who consistently presented higher salivary cortisol at 11 AM and/or 8 PM. There were no associations between salivary cortisol levels and ALM measures, either absolute or after correction to height squared (ALM index) or body mass index. GS was inversely correlated to sc-11AM (r = - 0.153, p < 0.001) and sc-8PM (r = - 0.118, p = 0.002). Each 10 nmol/l increase of sc-11AM, respectively sc-8PM, was associated with a GS decrease of 1.758 (SE 0.472) kg, respectively 2.929 (SE 1.115) kg. In postmenopausal women, sarcopenia is associated with higher salivary cortisol levels at 11 AM and 8 PM. An increase of daily free cortisol levels in the physiological range could participate to sarcopenia development by decreasing muscle function in postmenopausal women.