This study investigates the superhydrophobicity, antibacterial activity, and electromagnetic interference (EMI) shielding properties of cotton fabrics coated with Ag/PDMS. The effects of coating composition on these properties were analyzed, with special attention given to the relationship between surface roughness and the developed functionalities. The superhydrophobicity of the fabrics was assessed using water contact angle (WCA) and contact angle hysteresis (CAH) values, while antibacterial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that the surface roughness of the coated fibers, influenced by the concentrations of Ag NPs (0.2–4 g/L) and PDMS (20 and 40 g/L), affected the superhydrophobicity. The most superhydrophobic fabric (WCA 171°) was coated with a formulation containing 2 g/L Ag NPs and 20 g/L PDMS, and had the highest surface roughness. Increasing the concentrations of Ag NPs and PDMS deteriorated the optimum roughness. The coated fabrics showed efficacy against both types of bacteria, with Ag NPs content being the key factor in determining antibacterial performance. Testing the EMI shielding performance showed that increasing the concentrations of Ag NPs and PDMS enhanced the reflection coefficient (R) of fabrics against incident X-band electromagnetic (EM) waves by around 500%, due to the deposition of a higher amount of Ag NPs. The superhydrophobicity of fabrics was durable after 1000 abrasion cycles, and the fabrics retained their antibacterial activity even after numerous washings. The study also demonstrated that the Ag/PDMS coatings improved the thermal stability of cotton fabrics by increasing the decomposition onset temperature and remaining ash content. The coatings contributed to EMI shielding functionality by increasing the reflection coefficient. The Ag/PDMS coatings applied to cotton fabrics were durable and withstood 5 accelerated wash cycles and 1000 abrasion cycles. The results highlight the real role of Ag NPs and PDMS binder as coating ingredients in developing multifunctional surfaces for practical applications in antibacterial, superhydrophobic, and EMI shielding fields.This study investigates the superhydrophobicity, antibacterial activity, and electromagnetic interference (EMI) shielding properties of cotton fabrics coated with Ag/PDMS. The effects of coating composition on these properties were analyzed, with special attention given to the relationship between surface roughness and the developed functionalities. The superhydrophobicity of the fabrics was assessed using water contact angle (WCA) and contact angle hysteresis (CAH) values, while antibacterial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that the surface roughness of the coated fibers, influenced by the concentrations of Ag NPs (0.2–4 g/L) and PDMS (20 and 40 g/L), affected the superhydrophobicity. The most superhydrophobic fabric (WCA 171°) was coated with a formulation containing 2 g/L Ag NPs and 20 g/L PDMS, and had the highest surface roughness. Increasing the concentrations of Ag NPs and PDMS deteriorated the optimum roughness. The coated fabrics showed efficacy against both types of bacteria, with Ag NPs content being the key factor in determining antibacterial performance. Testing the EMI shielding performance showed that increasing the concentrations of Ag NPs and PDMS enhanced the reflection coefficient (R) of fabrics against incident X-band electromagnetic (EM) waves by around 500%, due to the deposition of a higher amount of Ag NPs. The superhydrophobicity of fabrics was durable after 1000 abrasion cycles, and the fabrics retained their antibacterial activity even after numerous washings. The study also demonstrated that the Ag/PDMS coatings improved the thermal stability of cotton fabrics by increasing the decomposition onset temperature and remaining ash content. The coatings contributed to EMI shielding functionality by increasing the reflection coefficient. The Ag/PDMS coatings applied to cotton fabrics were durable and withstood 5 accelerated wash cycles and 1000 abrasion cycles. The results highlight the real role of Ag NPs and PDMS binder as coating ingredients in developing multifunctional surfaces for practical applications in antibacterial, superhydrophobic, and EMI shielding fields.