The Hub, which is part of the business coalition Manchester Growth Company, was set up in 2011 to offer companies digital and financial support, as well as tailored support for textile and manufacturing businesses.
The PR contract will run for just over two years - from 21 December 2016 to 31 December 2018 - with an option to extend for an additional six months, the Hub said.
The successful agency will be expected to promote Greater Manchester and its businesses in a wide variety of industries, a spokesman for the Hub said. These could include agriculture, marketing and brewing - all sectors that the Hub has worked with previously.
The chosen agency will be expected to handle general media relations and offer editorial support, the Hub said.
Those wanting to pitch for the contract, which has an estimated value of £200,000, can do so via the organisation's website.