While many office workers experience low back pain (LBP), little is known about the effect of prolonged standing on LBP symptoms. This repeated-measures within-subjects study aimed to determine whether office workers with LBP are able to work at a standing workstation for one hour without exacerbating symptoms and whether using a footstool affects LBP severity. Sixteen office workers with LBP performed computer work at a standing workstation for one hour under the following two conditions, one week apart: with a footstool and without a footstool. The intensity of LBP was recorded at 10 min intervals. Maximal severity of LBP pain and change in LBP severity throughout the standing task were not different between the footstool and no footstool conditions (p > 0.26). There was a trend for more participants to have an increase in their pain between the start and end of the task when not using a footstool compared to using a footstool (p = 0.10). Most office workers with LBP are able to use a standing workstation without significant exacerbation of symptoms, but a proportion will experience a clinical meaningful increase in symptoms. Using a footstool does not change the severity of LBP experienced when using a standing workstation in individuals with a history of LBP.