Using natural tanning materials is needed to reduce toxicity of leather tanning industry. This investigation was carried out to evaluate the efficiency of using guava bark extract; Psidium guajava L. in leather tanning. The collected guava bark was dried at 25℃ for 5 days. Thereafter, the dried material was grounded for extraction using water at 90℃. Pickled pelts from 18 Barki rams aged 12-18 months were used and allocated randomly into 6 groups. The experimental groups were either guava extract separately or with using other re-tanning materials; chromium sulfate, aliphatic aldehyde, or phenol sulfonates. Extract characteristics, leather properties and scanning electron micrographs were determined. The results of extract characteristics showed the ability of using guava extract in leather tanning due to its values of extraction yield (54.24%), tannins content (21.36%), hide powder (31.12), and stiasny number (41.42). Although the properties of tanned leathers showed no preference in using the guava extract alone in tanning, but it could be more valuable when using as a re-tanning material to reduce chromium addition in mineral tanning or any other synthetic tanning materials to improve the quality of produced leathers.