Anxiety affects approximately 40 million American adults each year (Kessler, Chiu, Demler, and Walters, 2005; National Institute of Mental Health [NIMH], 2009). However, the dose-response research investigating the antianxiety and affective benefits of acute bouts of exercise indicates that multiple dose-response issues remain unresolved. The purpose of this study was to investigate the anxiolytic and affective responses following an acute bout of moderate intensity walking of different durations (30, 10 and 5 minutes) on a moderately fit, non-clinically anxious population. This study also sought to test the duration of effect by assessing post-exercise responses immediately and at 20 and 40 minutes post-exercise. This is the first study to include the analysis of four specific covariates (trait anxiety, fitness level, enjoyment of activity, and sex) when examining psychological responses to walking. One of the main findings of the current investigation was that a main effect of time was observed for the majority of variables. While some measures showed favorable (anxiety, tense arousal, calmness, tension, tranquility, physical exhaustion, affective valence, and revitalization) other measures ultimately showed unfavorable (positive affect, perceived activation, energetic arousal, energy, and positive engagement) responses following the cessation of exercise. Secondly, although several measures were affected by exercise duration (tranquility, physical exhaustion, and affective valence), the majority were not. Finally, of the four covariates, only fitness (positive affect, energetic arousal, and energy) and sex (positive affect, revitalization, energy, and calmness) influenced the exercise-affect relationship.