Background: Fractional exhaled nitric oxide (FeNO) is a noninvasive method to determine the degree of airway inflammation. Handheld devices such as the Vivatmo Me are used for home monitoring. Differences were found between the Vivatmo Me and standard measurements with the NIOX VERO. Therefore, we aimed to determine the accuracy of the Vivatmo Me for FeNO measurements. Methods: Adult patients with an appointment for FeNO-measurement according to regular care, were invited to perform the FeNO measurement with both devices. From these measurements the FeNO values were compared, and the device user-friendliness was determined. Results: One hundred and sixty-four patients were included. The number of attempts needed for a successful measurement and the failure rate were higher with the Vivatmo Me. Although the measurements were highly correlated, a significant difference (p < 0.001) was found between FeNO values measured with both devices. From the Vivatmo measurements, 32% did not fall within the claimed accuracy ranges. A linear correction on the FeNO values reduced this number. Conclusion: Our findings indicate that the Vivatmo Me does not comply with the claimed accuracy of clinical FeNO measurements and the measurement is challenging to perform. By applying the proposed correction, the comparative validity of the FeNO measurement improves and therefore its clinical usefulness.