The Facebook-owned instant messaging app began experiencing problems on Wednesday evening.
The issues began at around 9pm in the UK and then problems were reported in the US, South America and Asia, according to web service monitoring site Down Detector.
By 11.20pm many reported being able to access the service once again.
WhatsApp has not commented on the cause of the problem.
Social networking company Facebook bought WhatsApp for $19bn (£14.7bn) in 2014.