Acacia nilotica tree parts were analyzed for tannin content (condensed and hydrolysable) and protein precipitation ability. Leaves had higher hydrolysable tannin (HT) and barks had more condensed tannin (CT). HT contributed more to protein precipitation. CT was largely fiber-bound and resistant to decomposition. Negative correlation observed between total nitrogen and CT, while CT positively correlated with fiber-bound nitrogen and lignin. © 2012 Indian Academy of Wood Science. © 2012 Elsevier B.V., All rights reserved.