Our Leadership Team

Dedication to serving our policyholders starts at the top.
We strive to set standards of excellence for our entire organization.

Phil Gass
Chairman & Chief Executive Officer

Phil is a co-founder of Nassau and serves as chairman and chief executive officer. Learn more.

Kostas Cheliotis
General Counsel & COO

Kostas, also known as Gus, is a co-founder of Nassau and is responsible for legal affairs, strategy and corporate functions. Learn more.

Jacqueline Merl Bamman
Chief People Officer

Jackie is responsible for leading Nassau’s human capital strategy, focusing on initiatives that drive growth, innovation, culture, and the development and advancement of our employees. Learn more.

Thomas M. Buckingham, MAAA, FSA
Chief Product & Service Officer

Tom is responsible for all insurance product development, marketing and service-related functions. Learn more.

Edward W. Cassidy
Managing Principal of Saybrus Partners

Ed is managing principal of Saybrus Partners, Inc., Nassau's distribution company and has over 25 years of industry and sales management experience. Learn more.

David E. Czerniecki, CFA
Chief Investment Officer

David is responsible for setting investment strategy and overseeing Nassau’s investment portfolio. Learn more.

Diane R. Ellsworth
Chief of Staff

Diane is responsible for ensuring strategic initiatives are on track, working with the executive team and all business and staff areas, and coordinates communications with key stakeholders. Learn more.

Justin K. Mosbo
Chief Actuary & Chief Pricing Officer

Justin is responsible for all actuarial functions of Nassau along with all M&A transactions across insurance/reinsurance, asset management and distribution. Learn more.

Diana Piquette
Chief Financial Officer

Diana is responsible for the global finance function, providing oversight and leadership for financial planning, accounting and financial reporting, capital management, treasury, and tax. Learn more.

Vernon Young
Chief Risk Officer

Vernon is responsible for overall leadership and direction for enterprise risk management. Learn more.