The Leeds-based company will provide waste water network services to the utility for a minimum of three years.
The services will include emergency blockage clearance and remedial drainage work in the Thames Valley and North London.
Andy Brierley, a director, said: “This is our biggest win to date, and comes after a rigorous tender process which took 18 months of hard work and planning so obviously we are delighted.
“Thames Water is the biggest water and sewerage firm in the UK with 14 million customers so it is a huge coup for Lanes to have been awarded these prestigious contracts.
“The success reaffirms our position as market leader in the UK.”
The tender attracted more than 100 expressions of interest, said Mr Brierley.
The process saw the company pitted against major construction companies with large utility divisions.
Mr Brierley said around 180 staff would be needed to run the contracts.
Some of these will be transferred from existing contractors and some will be newly-created posts.
The majority will be based in Slough, Berkshire.
The Lanes Group is majority owned by the Earnshaw family from Rossendale in Lancashire.
In 1992, the family bought a £300,000-turnover business in Leeds called Lanes for Drains from businessman John Lane.
The company’s turnover has grown over the past two decades to £49m and it employs more than 760 people across 21 UK offices.
The management team has strong links to Yorkshire; joint managing director Graham Tattersall lives in Leeds, finance director David Nutton is from Wakefield and operations director Alan Wallis is from Rotherham.
Mr Brierley said: “Lanes continues to grow and capitalise on its reputation as the largest drainage contractor in the UK servicing all different types of industrial sectors.”
The company is focus its efforts on opportunities in the water sector resulting from new legislation.