Standing balance is an important motor task. Postural instability associated with age typically arises from deterioration of peripheral sensory systems. The modified Clinical Test of Sensory Integration for Balance and the Tandem test have been used to screen for balance. Timed tests present some limitations, whereas quantification of the motions of the center of pressure (CoP) with portable and inexpensive equipment may help to improve the sensitivity of these tests and give the possibility of widespread use. This study determines the validity and reliability of the Wii Balance Board (Wii BB) to quantify CoP motions during the mentioned tests. Thirty-seven older adults completed three repetitions of five balance conditions: eyes open, eyes closed, eyes open on a compliant surface, eyes closed on a compliant surface, and tandem stance, all performed on a force plate and a Wii BB simultaneously. Twenty participants repeated the trials for reliability purposes. CoP displacement was the main outcome measure. Regression analysis indicated that the Wii BB has excellent concurrent validity, and Bland–Altman plots showed good agreement between devices with small mean differences and no relationship between the difference and the mean. Intraclass correlation coefficients (ICCs) indicated modest-to-excellent test–retest reliability (ICC=0.64–0.85). Standard error of measurement and minimal detectable change were similar for both devices, except the ‘eyes closed’ condition, with greater standard error of measurement for the Wii BB. In conclusion, the Wii BB is shown to be a valid and reliable method to quantify CoP displacement in older adults.