The Star revealed Pilks intentions to invest heavily in the Cowley Hill plant back in April and the unanimous backing of planning councillors paves the way for the new development.
Pilkington, part of the Japanese NSG Group, won £5-million towards the project from the Government's Regional Growth Fund.
The total investment will create 50 skilled posts, protect existing jobs and allow the expansion of the company’s apprenticeship scheme.
Planning consent was also granted to demolish structures within the 56 hectare site.
The coating line is due to go live in October 2012 and will produce low emissivity glazing products which reduce the amount of heat lost through windows - and solar control glass.
Councillor Andy Bowden, cabinet member for regeneration, said: “This is a huge vote of confidence for St Helens from an international corporation.”