Hewitt was charged in January for engaging in offensive conduct towards a doping control official after he pushed a 60-year-old volunteer anti-doping chaperone following their semi-final loss to Italy last November.
Hewitt denied the charge and cited self-defence, but an independent tribunal upheld the charge, saying the Australian's behaviour was "not reasonable and proportionate" and that his actions did not meet the requirements of self-defence.
"Anti-doping personnel play a fundamental role behind the scenes in upholding the integrity of tennis, and they should be able to go about their roles without fear of physical contact," ITIA CEO Karen Moorhouse said in a statement.
"In this case, that line was clearly crossed, and we had no other option but to take action."
Hewitt's suspension, which will be effective from 24 September until 7 October, will prevent him from taking part in all tennis-related activities - including coaching, mentoring, playing, captaincy and other associated roles.
Australia host Belgium in the second round of qualifiers in Sydney from September 13-14 and the tribunal's chair Michael Heron said they did not want to be "unduly punitive" on Hewitt by impacting his Davis Cup schedule.
Hewitt, a former Wimbledon and US Open champion, may also appeal the decision, with the ITIA saying no appeal has been lodged yet.
