Actinidia arguta has recently gained considerable popularity among consumers due to the high nutritional value of its fruits, recognized as a rich source of bioactive compounds, including antioxidants. This study aimed to determine and compare the antioxidant activity (AA) of fruit extracts obtained from 10 different cultivars. The results of spectrophotometric assays were compared to those of effect-directed dot-blot and thin-layer chromatography (TLC). Total phenolic content (TPC) was determined spectrophotometrically (Folin–Ciocalteu) and verified through high-performance liquid chromatography and TLC. All studied extracts exhibited AA, although significant intracultivar differences were observed. Both spectrophotometric and chromatographic analyses consistently indicated the Vitikiwi and Geneva cultivars as having the highest antioxidant potential among the tested samples. However, chromatographic analyses revealed that the strong AA of the Vitikiwi was not associated with a high polyphenol content, but rather with its exceptionally high level of ascorbic acid, which led to an overestimation of phenolic content in the Folin–Ciocalteu assay. These findings demonstrate that AA in A. arguta fruits may result from different classes of bioactive compounds depending on the cultivar. The study emphasizes the importance of using both spectrophotometric and chromatographic methods to accurately evaluate antioxidant potential in plant-derived food products.