Aims To explore the effectiveness of an oral hygiene programme combined with home phone counselling on hepatitis C patients during antiviral treatment. Background Hepatitis C virus infection is the leading cause of liver diseases. Evidence indicates that the antiviral treatment for hepatitis C virus infection has been successful, albeit its many side effects, such as discomfort symptoms of oral ulcers, which, in turn, leads to discontinued treatment. Inappropriate oral hygiene may worsen the side effects and increase the risk of dropping out of the treatment. Design A quasi‐experimental pre–post‐test design was used. Methods The oral hygiene programme was based on a standardized protocol of oral health care combined with home phone counselling. The participants were recruited from an outpatient clinic between August 2016 and July 2017. The generalized estimating equation was used for repeated measures of oral health behaviour, oral health status and discomfort symptoms. Findings Thirty‐four participants completed this study. The findings indicated that the oral hygiene programme significantly improved tooth brushing, use of dental floss and oral comfort. The result showed that the participants’ oral health status significantly improved in 3 months. Conclusions This pilot study supports the finding that an oral hygiene programme can reduce oral discomfort, improve oral hygiene behaviour, and enhance the oral health status of hepatitis C patients receiving treatment. This is a simple and low‐cost programme, which can be performed at home easily and boosts the completion of antiviral treatment.