The new school is part of the £60.7 million multi-schools project, which is West Lothian's largest ever investment in education.
It will deliver two secondary schools and one primary school, as well as a shared sport, leisure and community facility.
Leader of West Lothian Council Lawrence Fitzpatrick welcomed Archbishop Leo Cushley, whose diocese of St Andrews and Edinburgh covers West Lothian, to mark the start of construction on the new school site.
Councillor Fitzpatrick said: "I'm delighted to see work begin on the fantastic new Sinclair Academy in Winchburgh.
"West Lothian has one of the best school estates in the country, and the new state-of-the-art school will ensure we have enough places for those who choose denominational education.
"Thanks to Archbishop Cushley for coming along to mark the start of construction of this important new facility, for the growing community of Winchburgh and the east of West Lothian."
Sinclair Academy is expected to open to pupils during 2023, and is named after the venerable Margaret Sinclair, who is revered for her work helping people through both trade unions and as a Sister of the Order of St. Clare.
Archbishop Leo Cushley said: "It's a huge pleasure to be invited along to see work start on the new Sinclair Academy in Winchburgh.
"Margaret Sinclair was a hugely inspirational figure during her short life, dedicating herself to supporting those in need.
"I hope the young people who attend the new Sinclair Academy will aspire to achieve their best in their lives, just like Margaret."
The project is being delivered on behalf of the council by its development partner Hub South East, with Morrison Construction as the primary contractor.
This is the same team who successfully delivered the award-winning West Calder High School, so have a strong track record in delivering new schools.
Scott Brown, Hub South East's Projects Director said: "It's exciting to mark the start of construction on-site for the new Sinclair Academy.
"We're proud to continue our successful partnership with West Lothian Council, and to be entrusted with its latest significant investment in education."
"We look forward to delivering this new secondary school alongside other schools in Winchburgh, realising a range of community benefits and ensuring social value for the local community during construction."
Eddie Robertson, Managing Director for Morrison Construction Building Central, commented: "We have been anticipating the start of this fantastic project for some time during the coronavirus pandemic and so we are delighted to be able to commence works.
"This new school will make such a difference to the community and it is very rewarding to be part of the team creating a facility to be proud of for local children."
The new schools are required as part of a £1 billion masterplan for Winchburgh which will deliver new greenspaces including the 78-acre Auldcathie District Park, a new canal marina, improved transport links, including a new railway station, and at least 3,800 new homes.
Over 5,000 new jobs are expected to be generated by the completion of the overall Winchburgh masterplan.
The schools project is partly funded with the support of a unique tri-partite agreement between West Lothian Council, The Scottish Government and Winchburgh Developments Ltd, a joint venture between West Coast Capital and CALA Homes.
