Both will sit on the agency's board to help support growth in the UK and overseas expansion.
Maguire was business development director for Europe at Anomaly and previously held the same role at digital marketing agency isobar. She has also worked at McCann London and CHI & Partners. Her appointment reflects W's aim to increasingly divert brand money from ad agencies into PR.
Tompkins joined W in 2012 as a director. As MD he will take responsibility for W’s UK P&L and operations, manage the agency's growth targets and oversee client work.
Maguire said: "During my career I have been drawn to some of the most pioneering creative agencies and I am absolutely delighted to have been asked to join W – an agency I have worked with, greatly admired and believe has the potential to set new standards in the creative industry for years to come."
Warren Johnson, W founder and CEO, added: "These two exciting appointments perfectly showcase our two-pronged talent strategy – promote from within and hire from outside the industry."
Earlier this year W produced a short film for the relaunch of the iconic Marmite brand.