The use of e-cigarettes has been banned in all hospitals and healthcare centres.
Health chiefs said they had no evidence over the long-term safety of the devices.
Dr Stephanie O'Keeffe, national director of health and well-being at the Health Service Executive (HSE), said the decision followed a detailed review of the safety and impact of e-cigarettes.
"The HSE can only recommend safe and effective products and strategies for quitting smoking, and there currently is no conclusive evidence that e-cigarettes are safe for long-term use, or are effective as a smoking cessation aid," she said.
"While we will keep this evidence under ongoing review, the e-cigarettes ban is being introduced as e-cigarettes pose a challenge to smoke-free campus enforcement and come with safety concerns for a healthcare environment."
The prohibition comes into effect on May 1.