BACKGROUND/OBJECTIVES: Continuous subcutaneous foslevodopa/foscarbidopa infusion (CSFLI) improves motor fluctuations in advanced Parkinson's disease (PD), but some patients continue to experience residual motor and non-motor fluctuations despite optimized infusion parameters. We describe two patients receiving CSFLI in whom the addition or reintroduction of opicapone was associated with improvement in persistent fluctuations. In one patient, clinical findings were further explored using wearable sensor monitoring. METHODS: Two patients with advanced PD treated with CSFLI and residual fluctuations received add-on opicapone. Clinical evaluation included neurological examination, assessment of motor fluctuations, and documentation of antiparkinsonian therapy before and after opicapone introduction. In one patient, motor performance was additionally evaluated with wearable sensor monitoring during the Timed Up and Go test and the 6-minute walk test before (T0) and three months after opicapone introduction (T1). RESULTS: In both cases, opicapone 50 mg once daily was associated with rapid improvement in residual motor and non-motor fluctuations during CSFLI therapy. In the first patient, freezing episodes and unpredictable akinesia resolved. In the second patient, the reintroduction of opicapone improved morning slowness, axial symptoms, and dorsal pain. Wearable sensor analysis showed increased walking distance during the 6-minute walk test, higher walking speed, reduced Timed Up and Go duration, increased step length, and reduced step length variability. CONCLUSIONS: These preliminary observations suggest that opicapone may deserve further investigation as a potential adjunctive strategy in selected patients receiving CSFLI who continue to experience residual fluctuations despite optimized infusion therapy. Wearable sensor monitoring may provide objective support for treatment assessment in this setting.