Mitogen-activated protein kinase (MAPK) cascades are one of the well studied signaling networks in plants. In this study a full length cDNA from Arachis hypogaea (peanut) encoding a mitogen-activated protein kinase was cloned using RACE-PCR approach. The cDNA was designated as AhMPK6 based on its high identity with AtMPK6 of Arabidopsis. The AhMPK6 encodes a 397 amino acid polypeptide that shows high similarity with MsSIMK, NtSIPK, OsSIPK of Medicago, tobacco and rice respectively. Phylogenetic analysis suggests that AhMPK6 belongs to the A2 subgroup of MAPK family. When expressed as a translational fusion with GFP, AhMPK6 displayed predominant nuclear localization. The conditional overexpression of AhMPK6 resulted in hypersensitive response (HR)-like cell death in tobacco, with a simultaneous upregulation of HR-marker gene transcripts and various defense response gene transcripts. The AhMPK6 induced gene expression suggests an overlapping or partially redundant function with previously reported AhMPK3.