The singer who shot into the charts after BBC's Fame Academy in 2002 will headline the celebrations in Plymouth on November 18.
Lemar will kick off the Plymouth Winter Festival with songs from his new album as well as old hits.
The London-born soul singer has sold more than two million albums and has won two BRITs and three MOBO awards.
The festive fun starts at 4pm with music and entertainment on the Heart Radio stage at the top of Cornwall Street.
The Urban X Dancers, Roo Mckeller, Zumba Zone and the Beatbreakers will be there to get the crowds warmed up before Lemar takes to the stage at 6pm.
He will be joined by ITV Westcountry to switch on the lights live on ITV1 at 6.20pm before local girl Lauren Francis, who made it through to this year’s X-Factor boot camp, will take to the stage to wrap things up.
The Christmas ice rink on the piazza and the Christmas Market in Armada way will also be opening their doors to coincide with the switch-on celebrations.
The Plymouth Winter Festival is packed with great events and activities for all the family
Late night shopping will run every Thursday from 18 November to 23 December, with most shops open until 9pm. In the week before Christmas (starting 20 December) most shops will be open every night until 8pm.
The festival will start with the Christmas Lights switch-on (Thursday 18 November) and features the Christmas ice rink on the piazza, festive shows at the Pavilions, Christmas markets (18 November to 2 January), Sleeping Beauty at the Theatre Royal (17 December to 22 January), the Christmas Carnival (5 December), late night shopping, street entertainment and a very special Santa fun run
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