Guava's bark contains tannin compound that can be used as an adsorbent. The purpose of thisstudy was to determine the optimum conditions of the adsorption of iron by the bark and its maximumabsorption capacity. The study was conducted by mass variation of bark for iron metal adsorption.The measurement of iron concentration which was not absorbed by the bark was conducted byatomic absorption spectrophotometer. The results showed that the adsorbent mass of 2.5 grams canabsorb 1.93mg/g with percent absorbance of 48.34%, and the maximum absorption capacity of ironlost at 4.98mg/g