Enzyme-treated asparagus extract (ETAS) has been developed as a novel anti-stress functional food ingredient that is produced from asparagus. Two human intervention trials with ETAS were conducted in healthy adult male volunteers. Study 1 was a randomized, double-blind, placebo-controlled study to assess the effects of ETAS on expression of heat shock protein 70 (HSP70) mRNA in blood and the autonomic nervous system (ANS). The ETAS group showed a tendency to enhance HSP70 mRNA expression level compared to the placebo group. Several ANS condition parameters were significantly improved in the ETAS group when compared to the placebo group. In Study 2, a randomized, double-blind, placebo-controlled, crossover trial investigated the influence on stress-related hormones and sleep. Serum and salivary cortisol levels were significantly elevated compared to baseline during the placebo period, but remained unchanged during the ETAS period. The salivary chromogranin A level was significantly decreased in the ETAS-treated subjects compared to their baseline levels. The actual sleep time was not significantly different between ETAS and placebo. However, when the subjects were divided into two categories based on sleep efficiency or the average of night sleeping time, ETAS intake was effective to modulate the sleep state among those with low sleep efficiency or excess sleep time.