Background: Poor adherence to the oral contraceptive pill (OCP) is reported as one of the main causes of unintended pregnancy in women that rely on this form of contraception. This study aims to estimate the associations between a range of well-established modifiable psychological factors and adherence to OCP.Method: A cross-sectional survey of 130 female University students currently using OCP (Mean age: 20.46 SD: 3.01, range 17-36) was conducted. An OCP specific Medication Adherence Report Scale was used to assess non-adherence. Psychological predictor measures included necessity and concern beliefs about OCP, intentions, perceived behavioural control (pbc), anticipated regret and action and coping planning. Multiple linear regression was used to analyse the data.Results: Fifty-two per cent of participants reported missing their OCP once or more per month and 14% twice or more per month. In bivariate analysis intentions (r = -0.25), perceived behavioural control (r = -0.66), anticipated regret (r = 0.20), concerns about OCP (r = 0.31), and action (r = -0.25) and coping (r = -0.28) planning were all significantly associated with adherence to OCP in the predicted direction. In a multivariate model almost half (48%) of the variation in OCP adherence could be explained. The strongest and only statistically significant predictors in this model were perceived behavioural control (beta=-0.62, p<0.01) and coping planning (beta =-0.23, p=0.03). A significant interaction between intentions and anticipated regret was also observed.Conclusion: The present data point to a number of key modifiable psychological determinants of OCP use. Future work will establish whether changing these variables results in better adherence to the OCP.