© 2020 by the authors. The benefits of park therapy have been investigated in young adults, but rarely for middle-aged and older adults. This study evaluates the physiological and psychological effects of walking in urban parks and park therapy images in winter, spring, and early summer. The experiments were implemented in two walking courses in the urban park in Japan and involved 12 middle-aged and older adults. Participants walked on walking courses in an urban park and city street for 11-15 min. Their heart rate and blood pressure were evaluated to determine physiological responses. The Profile of Mood States (POMS), State-Trait Anxiety Inventory (STAI), and Landscape Image Sketching Technique (LIST) were used to determine psychological responses and spatial conditions. Walking in an urban park exhibited lower heart rates and blood pressure as compared to walking in the city. It was congruent with lowered negative moods, total mood disturbance (TMD) scores, and state anxiety, while the higher positive mood was observed in the urban parks as compared to the city. Images in winter displayed trees, relaxation, and comfort; in spring, water, activity, people, surrounding place, and recreational space; and in early summer, greenery, lawn, and broadness. In conclusion, walking in urban parks leads to physiological, psychological relaxation, and varied landscape appreciation.