Sasser, who had led the company as CEO for 13 years, will move to executive chairman of the board. Sasser started at Dollar Tree in 1999 and was promoted to president and operating chief in 2001. In 2004, he assumed the CEO role.
Dollar Tree grew to $22 billion in revenue projected this year from $1 billion in revenue when Sasser took over. The chain also grew to 14,500 retail stores from 1,200 at the start of Sasser's tenure.
Philbin joined the company in 2001 before being promoted to chief operating officer in 2007 and president in 2013. In January, Philbin was moved to the position of enterprise president, heading responsibilities for both Dollar Tree and then newly-acquired Family Dollar operations.
Dollar Tree stock traded slightly down 0.57% to $83 premarket Monday.
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