Background: Quality of life in cancer patients might be affected by chemotherapy-induced toxicity. Especially in patients with pancreatic ductal adenocarcinoma (PDAC), with a short life expectancy, fear of poor quality of life is often a reason for both patients and medical oncologists to refrain from further treatment. In this study, we investigated quality of life (QoL), pain, sleep, and activity levels in locally advanced pancreatic cancer (LAPC) patients after FOLFIRINOX treatment. Methods: A total of 41 LAPC patients with stable disease or partial response were included after completion of at least four cycles of FOLFIRINOX. QoL was measured with the EORTC QLQ-C30 and NRS pain scores. Patients completed the Richards-Campbell Sleep Questionnaire (RCSQ) for five consecutive nights and wore a GENEActiv tri-axial accelerometer (Actiwatch) for 7 days, registering sleep duration, efficiency, and activity. Results: Mean EORTC QLQ-C30 score for global health status was 78.3 (± 17.3), higher than reference values for cancer patients (P < 0.001) and general population (P = 0.045). LAPC patients reported few disease-related symptoms. Two patients (5%) reported pain scores > 3. Mean sleep duration was 8 h/night (± 1.2 h) and sleep efficiency 70% (± 9%) with high patient-reported quality of sleep (mean RCSQ score 72.0 ± 11.4). Mean duration of moderate-vigorous activity was 37 min/week (± 103 min/week). Conclusions: QoL is very good in most LAPC patients with disease control after FOLFIRINOX, measured with validated questionnaires and Actiwatch registration. The fear of clinical deterioration after FOLFIRINOX is not substantiated by this study and should not be a reason to refrain from treatment. Trial registration: Dutch trial register NL7578.