The purpose of this research was to explore two ways of the application of chitosan, a biopolymer, for ink jet printing of textiles. 1) To apply chitosan as a post-treatment on the fabric ink jet printed with pigment based inks for the fixation of pigments on the fabric. 2) To incorporate chitosan as a binder in pigment based ink jet ink formulations. The incorporation of chitosan was carried out in two ways. 1) Direct addition of chitosan into the ink formulations containing surface modified pigments. 2) Preparation of chitosan encapsulated pigment nanoparticles using complex coacervation technique and using these nanoparticles for the formulation of ink jet ink. The degree of deacetylation (DD) was determined using FTIR spectroscopy. Various protocols proposed by researchers were used to determine the DD of chitosan samples used in the present study. The protocol proposed by Raut was found to be fairly accurate in determining the DD of chitosan samples. The molecular weight of chitosan was estimated using dilute solution viscometry method. The characterisation of the film forming ability of chitosan was evaluated using scanning electron microscopy (SEM). The colour strength (K/S), colour difference, colour characteristics and colour fastness to laundering and rubbing of ink jet printed fabrics post treated with chitosan were evaluated using standard methods. Post-treatment (pad-dry-cure method) of cotton fabric ink jet printed with pigment based inks revealed that chitosan could effectively fix the pigments on cotton compared to the commercial textile binders and the water-soluble derivative of chitosan. The chemical interaction between chitosan and cotton fabric was illustrated by FTIR-ATR analysis and through determination of carboxyl group content. The ink jet printed cotton fabric post treated with 3gpl chitosan (MW 156,156) maintained almost 86% of bacterial reduction against Klebsiella Pneumoniae even after 50 launderings. Inks containing chitosan were formulated and were found to be stable in terms of mean particle size and viscosity over a period of one month and for 4 freeze/thaw cycles. A magenta ink containing chitosan was selected for ink jet printing of cotton fabric. It was found that the DF was around 97% for magenta ink containing chitosan compared to around 53% fixation for magenta ink without chitosan on cotton fabric. Surface modified carbon black pigment with carboxylated (COO-) surface functionality was selected to prepare chitosan encapsulated pigment nanoparticles by complex coacervation technique. Chitosan encapsulated pigment nanoparticles with mean particle size diameter of 876 nm and 742 nm were formed when 5 ml of 0.1% w/v pigment was mixed with 2ml and 3ml of 0.1% w/v chitosan, respectively. However, no correlation was found between the particle size of the nanoparticles formed and the concentration of chitosan. The DF with ink containing chitosan encapsulated pigment nanoparticles was found to be around 98% while the blank ink with only surface modified carbon black pigment showed 44% fixation.