Background: Fibromyalgia symptoms have a significant impact on the ability to perform activities of daily living. These activities require the ability to perform two or more tasks at the same time, which is known as a dual task. Purpose: To analyze physical and cognitive performance differences between memory and arithmetic dual tasks. Methods: Twenty-five women with fibromyalgia participated in this study. Participants performed three physical tests (back scratch, arm curl, and 10-step stair) as a single task and under two types of dual task (memory and arithmetic). Results: Differences between the single and dual tasks were observed in the back scratch and the 10-step stair tests using the arithmetic dual-task. Significant differences were only observed for the memory dual-task in the 10-step stair test. In addition, the performance in the back scratch and in the 10-step stair was significantly lower under the arithmetic compared to the memory-based dual task. Furthermore, a significant difference between these two types of dual task was obtained in the dual-task cost of 10-step stair. Regarding cognitive performance, a significantly lower percentage of correct responses was found in the AbDT compared to the MbDT in the 10-step stair test. Conclusions: the AbDT could have a higher impact on physical performance than the MbDT during the back scratch and the 10-step stair tests. The characteristics of the sample, environment, complexity of the motor task, and difficulty of the simultaneous cognitive task may also be relevant for understanding the differences in dual-task interference.