Background: Because physical activity (PA) provides multiple medical and psychosocial benefits after a cancer diagnosis, greater integration of objective activity monitoring into research and clinical practice is warranted. Objectives: To review randomized PA trials in cancer survivors after diagnosis using an accelerometer or pedometer and make recommendations for integrating objective monitoring into research and practice. Major findings: 10 published PA and post-cancer diagnosis randomized trials have used pedometers (n=3), accelerometers (n=3), or both (n=4). Pedometers were primarily used to motivate PA adherence with several studies also using unblinded pedometers to assess the intervention effect on PA adherence. Accelerometers were primarily used to assess PA adherence after a PA intervention with one study using accelerometers to assess PA increase as a benefit of a non-PA intervention. One study used accelerometers to document sufficient ground forces for improving bone density in cancer survivors. Across studies, the reported objective monitoring outcome varied and was not always consistent with the stated intervention goal. Conclusions: PA and post-cancer diagnosis randomized trials have used objective monitoring primarily for motivation and/or adherence assessment. Investigators and practitioners are encouraged to expand the use of objective monitoring to also include understanding mechanisms of PA benefits and assessing non-PA treatment modality effects. Future clinical and research protocols should consider (1) the outcome to be measured and reported; (2) need (or not) for blinding of the instrument outputs to participants; (3) appropriateness of activity intensity cutpoints for interpreting accelerometer data; and (4) logistical issues relevant to cancer survivors after diagnosis.