He will report directly to the chief executive, Amanda Walsh, and will sit on the agency's executive management team, working alongside the chief strategy officer, Rebecca Morgan, the executive creative director, Ed Morris, the finance director, Ian Courts, and the chief marketing officer, Judy Mitchem.
In his new role, Nester-Smith will also run the agency's Unilever Sure, Innocent drinks and Twinings business.
Nester-Smith spent four years at RKCR/Y&R, where he worked on accounts that included Virgin Atlantic, Budweiser, The Home Office and COI. Before that, he was a board account director at Abbott Mead Vickers BBDO.
Walsh said: "We have found in Tom someone who shares our vision and enthusiasm for the future of the agency model. He will play a key role in helping us to evolve the skill-set of Lowe."