In this work, hydrophobic surfaces on cotton fabrics were obtained using a sol–gel technique to produce coatings applied using a spray of precursor solution followed by drying and heat treatments. Different types of treatments using the sol–gel process were performed in order to assess the influence on fabric hydrophobicity, with alteration of parameters including the concentrations of citric acid and tetraethyl orthosilicate (TEOS), the number of sprays, and curing of the fabric after obtaining the hydrophobic coating. The absorption of water into material samples were tested according to the AATCC test method 79. Scanning electron microscopy, contact angle, and Fourier-transform infrared spectroscopy (FT-IR) analysis were also studied. Excellent results were obtained for the contact angle (>150°), hence characterizing all the treatments as super-hydrophobic. FT-IR analyses revealed differences according to the citric acid concentration employed. The best results were obtained for samples treated using a higher concentration of citric acid and spraying the sol–gel solution twice. Mathematical models of the contact angle and the time for water absorption by the fabric treated with TEOS and citric acid showed good agreement with the experimental data. Highlights A hydrophobic coating on porous materials was achieved using a simple, single-step, and inexpensive procedure employing TEOS, citric acid, and ethanol, without any fluorinated compounds. The hydrophobic solution was applied using a spray of fine droplets released at a distance of 15 cm from the porous material. Better resistance to washing processes was obtained using higher concentrations of citric acid for formation of the hydrophobic solution employed for the porous coating on the cotton fabric.