Dianna O’Sullivan serves as both Chief Financial Officer and Controller at MSH. Since joining MSH in 2019, she has led key financial initiatives, including the successful implementation of the enterprise resource planning system and significant improvements to the month-end close cycle. Dianna became Interim Corporate Controller in 2022 and later assumed the role permanently. Under her leadership, MSH has enhanced the efficiency of its annual audits and tax filings. 

A Certified Public Accountant in Massachusetts, O’Sullivan brings a strong foundation in public accounting, having started her career as an auditor and tax preparer in Burlington, MA. She later held leadership roles in accounting and finance across the manufacturing, distribution, and professional services sectors. 

O’Sullivan holds a bachelor’s degree in business administration, accounting and management from the University of Massachusetts, Lowell and a master’s in accounting as well as a graduate certificate in taxation from Bentley University.