A simple sensing unit based on a disposable screen printed carbon electrode coated by an electrospun nylon-6 nanofibrous membrane was developed for in situ selective determination of ascorbic acid (AA) in different types of fruits. The membrane, prepared by electrospinning, represents a selective barrier to possible interferents, such as phenolic compounds, allowing an improved selectivity towards AA. No sample preparation and/or dilution is necessary since the new device is applied directly pricking the fruit with the electrode. A good correlation was obtained between the amperometric in situ method and a reference chromatographic methodology (HPLC-UV) when applied to various fruit samples.