The feature triggers the cross-platform messaging app which offers a free alternative to SMS texts.
HTC and Nokia have previously released handsets with Facebook-devoted buttons, but this marks a first for WhatsApp.
Analysts suggested the move would make WhatsApp the text app of choice on the handsets, but suggested it would have limited impact on the wider mobile phone market.
Nokia's Asha 210 runs on the firm's proprietary Series 40 operating system and will be targeted at consumers in emerging markets looking for a cheaper alternative to the Finnish firm's Windows Phone range and other companies' smartphones.
To achieve a targeted retail price of £47 ($72) Nokia decided that the device's 2.4in (6.1cm) screen would not be touch-enabled.
Users have to use its built-in Qwerty keyboard and navigation button to launch and operate apps, so having a dedicated key gives WhatsApp an edge over alternatives on the handset.
In addition owners of the phone are offered a subscription to the app for the device's lifespan rather than having to pay the normal annual fee.
Nokia refused to reveal the financial terms of the arrangement and said it would monitor customer response before deciding whether to include the feature on any of its other devices.
Nokia said it had not yet decided whether to offer the WhatsApp key on other handsets
Mr Joum did not give an equivalent figure of his own. However, he did say that WhatsApp processed about eight billion inbound messages and 12 billion outbound messages a day.
This can be a great success for Nokia Asha series as it may gain lot of popularity among the youth in countries like India.