In this study, we investigated the effect of an indoor plant on task performance and on mood. Three room arrangements were used as independent variables: a room with (1) a plant, or (2) a magazine rack with magazines placed in front of the participants, or (3) a room with neither of these objects. Undergraduate students (M= 35, F= 55) performed a task of associating up to 30 words with each of 20 specified words in a room with one of the three room arrangements. Task performance scores showed that female participants performed better in view of the plant in comparison to the magazine rack (p < 0.05). Moreover, mood was better with the plant or the magazine rack in the room compared to the no object condition (p < 0.05). However, the difference in task performance was highly influenced by the evaluation about the plant or the magazine rack. It is suggested that the compatibility between task demand and the environment is an important factor in facilitating task performances.