Eschscholtzia californica Cham. and Valeriana officinalis L. have long been used for the management of sleep disorders and anxiety. Use of a fixed combination of these two plant extracts (Phytostandard®d’Eschscholtzia et de Valeriane, PiLeJe Laboratoire, France) was investigated in an observational study. Adults with adjustment insomnia according to the criteria of the International Classification of Sleep Disorders and with an insomnia severity index (ISI) score >7 enrolled by GPs took a maximum of four tablets of the eschscholtzia and valerian combination every night for four weeks. Within one month, ISI score decreased by approximately 30% (from 16.09 ± 3.67 at inclusion (V1) to 11.32 ± 4.78 at 4 weeks(V2); p < 0.0001). Night sleep duration significantly increased between the first and the fourth week of supplement intake, sleep efficiency increasing from 78.4% ± 12.5 to 84.6% ± 10.2 (p ¼ 0.002). There was no improvement in sleep latency. The number of awakenings decreased by approximately 25% and their total duration by approximately 25 min. Anxiety score significantly decreased by 50% from 13.9 ± 7.3 at V1 to 6.7 ± 6.3 at V2 (p < 0.0001). The supplement was well tolerated. These results suggest that the tested combination of eschscholtzia and valerian extracts could be beneficial for the management of insomnia in adults and deserves further investigation