The direct arylation of aliphatic aldehydes has been established via Pd-catalyzed sp(3) C-H bond functionalization in the presence of 3-aminopropanoic acids as transient directing gronps. The reaction showed excellent functional group compatibility and chemoselectivity in which a predominant preference for functionalizing unactivated beta-C-H bonds of methyl groups over others was athieved. In addition, C-H bonds of unactivated secondary sp(3) carbons can also lie functionalized. The extreme popularity and importance of aliphatic aldehydes would result in broad applications of this novel method in organic chemistry and medicinal sciences.