The aim of this pilot study was to investigate the impact of the direct treatment of perfectionism on the outcome of perfectionism and eating disorder pathology. Sixty-one participants, attending day hospital treatment, participated in a randomised controlled study, in which treatment as usual (TAU) was compared with TAU combined with a clinician-lead cognitive behavioural treatment for perfectionism (TAU-+-P). Linear mixed model analysis revealed no significant interaction effects but significant main effects for time on variables measuring eating pathology and perfectionism. Outcomes supported the effectiveness of overall treatment but suggested that adding direct treatment of perfectionism did not enhance treatment. The results are discussed in relation to the existing literature on the treatment of perfectionism.