Background. Accumulating evidence supports leukocyte telomere length (LTL) as a biological marker of cellular aging. Poor sleep is a risk factor for age-related disease; however, the extent to which sleep accounts for variation in LTL is unknown. Methods. The present study examined associations of self-reported sleep duration, onset latency, and subjective quality with LTL in a community-dwelling sample of 245 healthy women in midlife (aged 49-66 years). Results. While sleep duration and onset latency were unrelated to LTL, women reporting poorer sleep quality displayed shorter LTL (r = 0.14, P = 0.03), independent of age, BMI, race, and income (b = 55.48, SE = 27.43, P = 0.04). When analyses were restricted to participants for whom sleep patterns were chronic, poorer sleep quality predicted shorter LTL independent of covariates and perceived psychological stress. Conclusions. This study provides the first evidence that poor sleep quality explains significant variation in LTL, a marker of cellular aging.