We examined the association of objectively measured sedentary time (ST) and physical activity (PA) levels with pain, fatigue, and the impact of the disease in women with fibromyalgia. Four hundred and nineteen (mean age +/- SD=51.7 +/- 7.6years old) women with fibromyalgia participated. ST and PA levels (light, moderate, and moderate-to-vigorous [MVPA]) were measured with triaxial accelerometry. We assessed experimental pain with algometry and clinical pain, fatigue, and impact of fibromyalgia with a number of questionnaires. The association of ST and light PA with most of the pain- and fatigue-related outcomes and impact of fibromyalgia (all, P0.019) was independent of moderate and vigorous PA. Furthermore, the association of vigorous PA with general and physical fatigue was independent of ST and light and moderate PA (all, P<0.001). In conclusion, lower levels of ST or higher levels of light PA are associated with lower pain, fatigue, and the overall impact of the disease independent of moderate and vigorous PA in women with fibromyalgia. Interestingly, higher vigorous PA is independently associated with lower general and physical fatigue. These results are significant for future ST and PA intervention studies in this population.