Slime molds, though morphologically similar to fungi, are protists and exhibit a range of colors including red, brown, yellow, and blue. They are commonly found in moist environments rich in decaying organic matter, such as leaf litter, wood, and agricultural or forest waste. Slime molds are classified into two major types: cellular and acellular. Their life cycle includes two distinct stages: an amoeboid feeding stage, during which they consume bacteria, fungi, and organic debris, and a fruiting stage that resembles a fungal structure. Recently, slime molds have gained importance as a source of new bioactive compounds. Several metabolites, such as naphthoquinones, pyrones, tetramic acid derivatives, and physarochrome, have been reported from several slime molds and their fruiting bodies. While associated endosymbiotic bacteria have been reported, they remain comparatively underexplored. This chapter focuses on the isolation of endosymbionts from slime mold fruiting bodies, with the aim of elucidating their role in the host’s life cycle and secondary metabolite production.