While internet-based cognitive behaviour therapy (iCBT) programs for mental health conditions has a demonstrated evidence base, the application of iCBT to those experiencing cancer-related distress has not been reported. This study therefore developed and pilot tested a self-guided iCBT program for patients with early stage cancer. Cancer Coping Online is a 6-week intervention which provides information, worksheets, and activities to address commonly experienced physical, emotional, social and communication difficulties. Participants were 12 patients (11 female) recruited over a 3-month period from one public hospital. The primary outcome measures were negative affect and posttraumatic stress. The secondary outcome measures were coping styles (helplessness/hopelessness, anxious preoccupation, cognitive avoidance, fatalism and fighting spirit). Changes over time were measured using within group effect sizes (Cohen’s d), with reliable change indices (RCIs) used to assess the clinical significance of changes over time. The intervention lead to reductions in negative affect (d=0.53), helplessness/hopelessness (d=0.64), anxious preoccupation (d=0.43), and fatalism (d=0.42). These reductions were clinically significant for 33% of the sample for negative affect, and for 25% of the sample for helplessness/hopelessness and anxious preoccupation. These results indicate that an iCBT program for cancer patients can reduce distress, and warrant further investigation through a randomised controlled trial.