WATER insoluble organic pigments presented by vat dyes were …… converted to the soluble leuco form through reduction using different reducing agents. The latter include Glucose, β-Cyclodextrin, sodium sulfoxylate formaldehyde (Rongalite C), and Redoxal Z reducing agent based on zinc sulfoxylate. The leuco form was then submitted to sudden oxidation using sodium perborate in presence of acetic acid under sonication. The obtained nano-sized pigment particles were used for printing cotton fabrics , and the color strength (K/S) of the prints were monitored. Results disclose that the K/S values for nanopigment prepared under Cyclodextrin reduction are nearly the same, if not higher than those obtained using sulfer-based reducing agents (Rongalate and Redoxal), while Glucose brings about the lowest K/S values. Four vat dyes have been used in the current work, and results of concern verify that the size of nanopigment obtained and the colour strength values (K/S) are manifestation of nature of the dye including molecular size and structure and molecular configuration. Regardless of the type of reducing agent used and/or the method of fixation, the highest K/S values are obtained with nanopigment dispersion prepared using 125g/L reducing agent at pH 7. Under these conditions, a homogeneous morphology with quite uniform particle size distribution in the range of 6-16 nm could be achieved vis-á-via 160-280nm for the blank Cibanon Golden Yellow RK vat dye.