Abstract Background COVID-19 public health measures like handwashing and social distancing can help stem the spread of the virus. Adherence to guidelines varies between individuals. This study aims to identify predictors of non-adherence to social distancing and handwashing guidelines. Methods A cross-sectional weekly telephone survey was conducted over eight weeks (11/06/2020–05/08/2020). The sample included adults resident on the island of Ireland (75:25 split between ROI and NI). Data were collected on demographics, threat perceptions, fear of COVID-19, response efficacy and self-efficacy, response cost and social norms, COVID-19 behaviours, mood, loneliness, and self-reported health. Results 3011 participants were surveyed. Handwashing non-adherers were more likely to be male (OR: 5.2, 95% CI: 2.4 – 11.3), to have higher levels of loneliness (OR: 1.86, 95% CI: 1.1 – 3.1), and higher perceptions of handwashing costs (OR: 3.4, 95% CI: 2.2 – 5.2). Those reporting rarely engaging in social distancing were more likely to be members of lower socioeconomic groups, to be younger (OR: 0.97, 95% CI: 0.96 – 0.98), male (OR: 1.67, 95% CI: 1.1 – 2.5), healthcare workers (OR: 1.98, 95% CI: 1.1 – 3.4), to report lower mood (OR: 1.72, 95% CI: 1.3 – 2.2), were less likely to live in households with people aged under-18 (OR: 0.75, 95% CI: 0.6 – 0.9), and to have lower fear of COVID-19 (OR: 0.79, 95% CI: 0.6 – 0.9). Conclusions Non-adherers to handwashing differ to social distancing non-adherers. Public health messages should target specific demographic groups and different messages are necessary to improve adherence to each behaviour.