Background Nurses may be well poised for providing physical activity guidance and support to patients. Purpose The purposes of this study were to examine the effectiveness of a concise, evidence based online learning modules strategy (OLMS) for improving nurses’ physical activity counselling. Methods 68 nurses were randomly assigned to either an OLMS group or control group. The OLMS group completed a series of six online learning modules aimed at improving physical activity counselling practice. Results The OLMS group, compared to the control group, showed a trend for improvement in Physical Activity Counselling Practice ( p = .063) after controlling for baseline values, and significant improvement in (a) Self-efficacy for Physical Activity Counselling ( p = .001), (b) Knowledge of Physical Activity Guidelines, ( p = .031), and (c) Perceived Benefits of Physical Activity Counselling ( p = .014) over the course of the intervention. No significant change was found for Barriers for Providing Physical Activity Counselling ( p > .05). Conclusions The OLMS tested may be an effective means for improving self-efficacy, knowledge, and perceived benefits of physical activity counselling, suggesting the utility of online learning strategies for improving nurses’ physical activity counselling practice. Given barriers to providing physical activity counselling were not affected by the intervention, future interventions and policy change could target these barriers specifically in order to give nurses more tools and time for reaching patients and addressing physical activity counselling in practice.