A deal could value the company at, at least $9 billion, Bloomberg reported citing people with knowledge of the matter.
WhatsApp rolls out major update for iPhone users
Slack is a platform where employees can send messages, collaborate, organise and share files. The technology also integrates with a wide variety of business software - such as Salesforce.com Inc and Microsoft Corp's Skype - so employees can do all their work within Slack.
San Francisco-based Slack has raised more than $500 million from venture capitalists and was valued at $3.8 billion at its last private financing round a year ago.
Skype draws inspiration from Snapchat in big redesign
Both Amazon and Slack were not immediately available to comment outside of regular US business hours.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ