After completing a city management internship in Carbondale, Illinois, Thomas Marko moved to Florida, where he began a lengthy career with Miami-Dade County. He began as an Administrative Officer 1 in the Public Works Department, helping to manage the solid waste program that served more than 2 million citizens. He helped with the budget, procurement, and contracts and prepared ordinances relating to landfills, transfer stations, and recycling. Thomas Marko earned promotions and became an Administrative Officer 2 and then Administrative Officer 3, gaining more responsibility and taking on supervisory roles.

After five years as an Administrative Officer, Thomas Marko found employment as Miami-Dade County's Director with the Consumer Services Department in the Passenger Transportation Regulation Division. Countywide in Miami-Dade, he managed the for-hire industry, which included taxis, limos, tourist vans, and private school buses, as well as a staff of 30. Thomas Marko made long-lasting impacts by enforcing reform and improving the division’s financial stability, information technology systems, and processes. He also drafted County ordinances and resolutions.

Thomas Marko then spent six years in employment outside of the County before returning in 2000 to become a Senior Budget Analyst for the Office of Management and Budget. Within the County's $7 billion budget, Marko advised on matters relating to the budget, policy, and management for the Budget Director. He provided solutions for matters relating to finances, operations, and the budget while helping ensure that County operations stayed within established parameters. Thomas Marko coordinated with the County's official business attraction and expansion partner, the Beacon Council, helping bring new businesses to the County and adding to local job creation.

Today, Thomas Marko serves as Miami-Dade County's Development Coordinator in the Office of the Mayor. He expedites approvals for land use and development and associated business start-ups across the County. Since occupying this position in 2005, Marko has helped the local economy save millions of dollars in both private and public projects.