HIV is a major threat to the people of the rural Amhara Region, northwest Ethiopia. To date, numerous studies have focused on condom use for HIV prevention. Using the theory of planned behaviour, this study investigates the psychosocial determinants of intended sexual faithfulness among rural males in the Amhara Region. In February 2008, we conducted a cross-sectional study with 100 males, with an age range of 20–50 years (mean age 38 years), in Dejen Woreda. The participants were illiterate or had a low level of literacy and all were rural farmers. Consequently, 10 literate male data collectors were recruited from the same community to assist in collecting data by means of a structured questionnaire. In the analysis of social cognitions as determinants of sexual faithfulness, attitude to faithfulness emerged as the best predictor of intended faithfulness, with significant contributions from self-efficacy and social norm for faithfulness. Thus, balanced and comprehensive HIV interventions focusing on attitudes, self-efficacy and social norms pertaining to faithfulness, sexual abstinence and condom use are needed to halt the spread of HIV among low-literate males in rural Amhara.