Greenhouses in hot and humid regions present significant challenges in maintaining optimal temperatures and humidity while minimizing energy and water usage. Traditional boiler-based heating is energy-intensive, and evaporative cooling often fails to maintain suitable conditions, especially under high humidity and peak thermal loads. This study evaluates the performance of a novel hybrid geothermal heat pump (HGSHP) system integrated with a cooling tower, specifically optimized for greenhouse operations in hot and humid climates such as Houston, Texas. The system was assessed using a dynamic model developed in TRNSYS Studio. Results showed that the HGSHP configuration reduced cooling energy consumption by up to 10.8% compared to GSHP-only systems and significantly enhanced ground thermal stability, lowering the annual ground temperature rise from 1 °C to less than 0.1 °C. The wet cooling tower effectively mitigated thermal imbalance by rejecting up to 37% of the cooling load during peak summer conditions. These findings highlight the potential of HGSHP systems to deliver efficient heating, cooling, and dehumidification with improved energy performance and long-term sustainability for greenhouse applications in hot and humid regions.