A total of 157 women with fibromyalgia were randomized to receive motivational intervention plus implementation intention intervention (n=51), implementation intention intervention only (n=43), or control (i.e., postural hygiene education; n=63). The primary outcomes of interest were the adherence to a minimum walking program, adherence to a standard walking program, and walking behaviour steps. Secondary outcomes of interest included fibromyalgia impact, pain intensity, and distress. Outcomes were assessed at 7, 12, and 36 weeks post-intervention. Results revealed adherence to the minimum walking program and the standard walking program were associated with the combination group (p<0.001), suggesting a benefit with the combination intervention. No significant associations were observed in any group in the walking behaviour steps outcome. Physical function was also associated with the combination group (p<0.05); however, no significant interactions were observed for fibromyalgia impact, pain intensity, or distress in any of the treatment groups.