Xyloglucan isolated and purified from tamarind seed was subjected to various degrees of γ-irradiation treatments, from 10 to 70 kGy, monitored for radiation damage and then studied using a new combined hydrodynamic approach with regards to conformation and flexibility. Radiation products were analysed with regard to molecular weight (weight average) Mw from size exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLs), intrinsic viscosity [η] and sedimentation coefficient so20,w. Sedimentation coefficient distributions and elution profiles from SEC-MALLs confirmed the unimodal nature of the molecular weight distribution for each sample in solution. The chain flexibility was then investigated in terms of the persistence length, Lp of the equivalent worm-like chain model. The traditional Bushin-Bohdanecky (intrinsic viscosity) and Yamakawa-Fujii (sedimentation coefficient) relations were used separately then combined together by minimisation of a target function according to a recently published procedure [Ortega, A., & García de la Torre, J. (2007). Equivalent radii and ratios of radii from solution properties as indicators of macromolecular conformation, shape, and flexibility. Biomacromolecules, 8, 2464-2475 [see also Ortega, A. Metodologías computacionales para propiedades en disolución de macromoléculas rígidas y flexibles. Ph.D. Dissertation, Universidad de Murcia, 2005]] and yielded an estimate for Lp in the range 4-9 nm using floated and fixed mass per unit length analysis protocols and "point" global analysis: irradiated xyloglucans behave as flexible structures in common with pressure/heat treated materials.