Research Highlights: This study demonstrated that viewing forest landscapes induced physical and mental health benefits on young women. Background and Objectives: The health-promoting effects of spending time in forests have received increasing attention; however, there is a lack of evidence-based research investigating the effects of spending time in forests on women. This study aimed to evaluate the physiological and psychological effects of viewing forest landscapes on young women. Materials and Methods: The experiments were conducted in six forests and six city areas and included 65 women (mean age, 21.0 ± 1.3 years). Participants viewed a forest and a city area for 15 min, during which their heart rate variability and heart rate were measured continuously. Blood pressure and pulse rate were measured before and after the viewing. After the viewing, participants’ psychological responses were assessed using the modified semantic differential method, Profile of Mood States (POMS), and the State–Trait Anxiety Inventory (STAI). Results: Compared with viewing city areas, viewing forest landscapes was associated with significantly higher parasympathetic nervous activity and lower sympathetic nervous activity and heart rate. Moreover, scores of the comfortable, relaxed, and natural parameters and vigor subscales of POMS were significantly higher with forest viewing. The scores of negative feelings, such as tension–anxiety, depression–dejection, anger–hostility, fatigue, and confusion, were significantly lower, as were scores for the total mood disturbance observed using POMS and the anxiety dimension observed using STAI. Conclusions: Viewing forest landscapes resulted in physiological and psychological relaxations in young women.