Menopause is associated with adverse changes in coagulation homeostasis. We aimed to investigate the association between objectively measured sedentary behavior (SB) and SB bouts (i.e., number and length of SB bouts) vs. fibrinogen levels in post-menopausal women. Fifty-three post-menopausal women (age 59.8 ± 6.2 years, BMI 27.3 ± 4.4) wore a multisensory device (Sensewear Mini Armband, BodyMedia, Inc., Pittsburgh, PA) for 5 days, to measure SB and physical activity (PA). Blood samples were collected to measure serum fibrinogen. Fibrinogen was directly correlated with SB (r = −0.48, p < 0.01), lying down during awake time (r = −0.50, p < 0.01), and both medium (11–30 mins) and very long bouts (>1 h) of SB (r = −0.59, p < 0.01; r = −0.51, p < 0.01, respectively), and inversely correlated with moderate to vigorous-intensity physical activity (r = −0.39, p < 0.01). Furthermore, fibrinogen was also directly correlated with BMI (r = −0.28, p < 0.05). In postmenopausal women without prevalent cardiovascular disease, the number of prolonged and uninterrupted sedentary bouts is directly correlated with increased fibrinogen levels, regardless of PA and BMI. This result suggests the importance of delivering new strategies to counteract the increase of sedentariness and inactivity of the postmenopausal population.