Objectives. To investigate the six-week influence of acupuncture on sleep quality and daytime functioning in primary insomnia. Methods. The study was a double-dummy, single-blinded, randomized, placebo-controlled clinical trial. A total of 180 patients with primary insomnia were randomly assigned to 3 groups: verum group underwent verum acupuncture plus placebo; estazolam group underwent estazolam plus sham acupuncture; sham group underwent sham acupuncture plus placebo. The outcome was measured by Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and the 36-item short-form health survey (SF-36). Results. The three groups showed significant improvement compared with the pretreatment baseline. Compared with the other two groups, the verum group reported improved sleep quality (SQ) and vitality (VT), decreased daytime dysfunction (DD) and sleepiness (ESS score). The differences were kept from the treatment period to the end of the trial. Discussion. Verum acupuncture appeared to be more effective in increasing sleep quality and daytime functioning than sham acupuncture and estazolam. Trial Registration. The trial is registeded with ClinicalTrials.gov ISRCTN12585433.