The project, which had been stalled due to land acquisition problems, will cost Rs 3,263 crore.
"Despite the initial hurdle, the Kerala stretch of the project will gain impetus with commencement of 100 per cent construction work," the company said in a statement.
The pipeline, which forms part of the National Gas Grid, will be completed by December 2018.
GAIL said contracts for pipeline laying works for the 111-km stretch falling in Malappuram, Kannur and Kasargod districts have been awarded.
The Kochi-Koottanad-Mangaluru pipeline will give a major economic boost to Kerala by way of supplying environment-friendly industrial development.
In Phase-I of the project, around 41-km pipeline had already been commissioned during 2013 to transport natural gas from Kochi LNG Terminal. Currently, around 2.6 million standard cubic meters per day of gas is being supplied to various consumers in and around Kochi city, the statement added.