Mangrove ecosystems, defined by extreme conditions such as fluctuating salinity, pH, temperature, and moisture levels, consist of unique microbial communities. This chapter emphasizes the molecular interactions between mangrove fungi and their environment. The usage of different molecular techniques such as DNA sequencing and metagenomics reveals the genetic and physiological adaptations that enable the survival of various microorganisms. Aspergillus terreus, isolated from hydrothermal vents, showcases upregulation of genes associated with stress tolerance, allowing it to endure high temperatures, acidic pH, and high salinity. Similarly, Halophytophthora spp. demonstrate salinity tolerance and nutrient uptake capabilities, crucial for their persistence in mangrove habitats. These adaptations are explored through molecular markers such as the internal transcribed spacer region and stress-responsive gene analysis. Host specificity also plays a critical role in fungal diversity, with species like Phomopsis mangrovei and Fusarium spp. forming symbiotic relationships with mangrove trees such as Rhizophora apiculata and Avicennia marina. These interactions improve nutrient cycling and plant resilience. The study highlights the potential of mangrove fungi in bioremediation and its ability to degrade hydrocarbons and in the removal of heavy metals in the environment. Understanding these molecular interactions provides valuable insights into the ecological roles and biotechnological applications of mangrove-associated fungi and its need for their conservation.