Objective: Dietary soy may improve menopausal symptoms, and subsequently mediate mood. This novel study examines various does of dietary soy drink on everyday mood stability and variability in postmenopausal women. Methods: Community dwelling women (n=101), within 7 years post menopause consumed daily either a low (10mg, n=35), medium (35mg, n=37) or high (60mg, n=29) dose of isoflavones, for twelve weeks. Menopausal symptoms and repeated measures of everyday Mood (Positive (PA) and Negative (NA) affect) (assessed at four time points per day for four consecutive days, using PANAS) were completed at baseline and follow up. Results: The dietary soy intervention had no effect on everyday mood stability (for PA (F(2,70) = .95, p = .390) and NA (F(2,70) = 0.72, p = .489) or variability (for PA (F(2,70) = .21, p = .807) and for NA (F(2,70) = .15, p=.864) or on menopausal symptoms (for vasomotor (F (2,89) = 2.83, p = .064), psychological (F (2,88) = 0.63, p = .535), somatic (F (2,89) = 0.32, p =.729) and total menopausal symptoms (F (2,86) = 0.79, p = .458)). There were between group differences with the medium dose reporting higher PA (low, mean: 24.2, SD: 6 and medium, mean: 29.7, SD: 6) and the low dose reporting higher NA (P = 0. 048) (Low, mean: 11.6, SD: 2 and high, mean: 10.6, SD: 1) in mood scores. Psychological (baseline M = 18 and follow up M = 16.5) and vasomotor (baseline M = 4.2 and follow up M = 3.6) scores declined from baseline to follow up for the overall sample. Conclusions: Soy isoflavones had no effect on mood at any of the doses tested. Future research should focus on the menopausal transition from peri to post menopause as there may be a window of vulnerability, with fluctuating hormones and increased symptoms which may affect mood.