Stress and anxiety are interconnected, sharing both behavioural and neural foundations. Ashwagandha (Withania somnifera) helps reduce stress and anxiety. This study aimed to evaluate the efficacy and safety of a proprietary herbal extract of ashwagandha root (APB) in adult men and women with moderate stress and anxiety. This 8-week, randomized, double-blind, three-arm, placebo-controlled trial included 141 healthy men and women aged 18–65 years with stress and anxiety. Participants were randomized to receive either 300 mg of APB twice daily (n = 47), ashwagandha root extract (ARE, n = 47), or placebo (PL, n = 47) for 8 weeks. The primary endpoint was a change in serum cortisol levels at week 8. Secondary endpoints were the mean changes in Perceived Stress Scale (PSS), Hamilton Anxiety Rating Scale (HAM-A), Profile of Mood States (POMS), and Oxford Happiness Questionnaire (OHQ) scores. Safety was assessed through clinical adverse events (AEs) and laboratory parameters. Between-group comparisons were analyzed using one-way ANOVA with Tukey’s post-hoc test, and within-group changes were assessed using paired t-tests. At 8 weeks, all groups have shown a significant reduction in serum cortisol, and improvements in PSS (P < 0.0001), HAM-A (P = 0.001), and POMS domain scores (tension, depression, and anger, P < 0.0001). In addition, the APB showed significant differences compared with ARE and PL for PSS, HAM-A total score, OHQ, and POMS (P < 0.05). The proprietary herbal extract of ashwagandha root (300mg twice daily) is considered an effective and safe intervention for reducing stress and anxiety.