Sears, 43, is a former Kenyan Cricket chief executive who has worked in sports administration since the 1990s.
His CV includes commercial and communications roles with the Rugby Football Union and Northampton Saints but since 2000 he has focused on cricket.
He was the commercial director at Worcestershire County Cricket Club between 2000 and 2005 and then spent three years as chief executive with Derbyshire County Cricket Club.
Philip Browne, IRFU chief executive, is hoping Sears' experience of building sports teams will translate into more success on the pitch.
"Throughout his career, Tom (Sears) has, time and again, shown his ability to develop and grow each professional sports organisation with whom he has worked," said Browne.
"This was certainly something that appealed to the panel conducting the interview process.
"The position attracted an exceptionally high level of interest, proving yet again how far Connacht has progressed.
"There is real scope to develop Connacht Rugby at all levels and ensure the province is at the forefront of Irish and European rugby in the coming years.
"There is no reason why Connacht can't develop into one of Europe's leading sides and that will be our collective goal."
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