An aqueous water repellent useful in the treatment of substrates of lignocellulose-origin materials or the like is characterized by comprising the product of co-hydrolytic condensation of (A) 100 parts by weight of an organosilicon compound having the formula:
(R1)a(OR2)bSiO(4-a-b)/2 (1)
wherein R1 is alkyl, R2 is alkyl, 0.75≦a≦1.5, 0.2≦b≦3 and 0.9<a+b≦4, and (B) 0.5-49 parts by weight of an amino-containing alkoxysilane having the formula:
R3R4NR5—SiR6n(OR2)3-n (2)
wherein R3 and R4 are H or alkyl or aminoalkyl, R5 is a divalent hydrocarbon group, R6 is alkyl, and n is 0 or 1, or a partial hydrolyzate thereof in the presence of an organic acid or inorganic acid.