Doug McCullough

Mergers & Acquisitions Attorney | Houston & Dallas, Texas

Doug McCullough is a Texas mergers and acquisitions attorney representing both sellers and buyers in complex, high-impact corporate transactions. A founding partner of McCullough Sudan PLLC, now Vanguard Legal, PLLC, Doug brings extensive experience in tax-efficient M&A, investment structuring, and financial transactions, supported by an advanced Master of Laws (LL.M.) in Taxation.

Doug advises clients on both domestic and cross-border transactions, frequently working with global companies expanding into the United States. His practice emphasizes international corporate and tax planning, helping foreign investors and multinational businesses minimize U.S. tax exposure, ensure compliance, and adapt their operations to the American legal environment.

His industry experience spans energy, oilfield and offshore services, manufacturing, engineering and environmental services, technology, medical devices, and healthcare. Doug’s collaborative approach and entrepreneurial mindset enable him to serve not just as legal counsel, but as a strategic partner in business growth and development.

As the founder and managing partner of a corporate transactions law firm for nearly a decade, Doug has advised private investors, venture capital firms, and private equity groups on transactions that create long-term value and drive organizational success.

Doug earned his LL.M. in Taxation from Southern Methodist University School of Law and his Juris Doctor from Texas Tech University School of Law. He holds a bachelor’s degree from Indiana University.

Outside of his legal practice, Doug enjoys hiking, spending time outdoors with his family, and exploring his passion for genealogy. A dedicated endurance athlete, he has completed nine marathons and continues to bring that same focus and determination to his professional work.