Proteins bearing a SET domain have been shown to methylate lysine residues in histones and contribute to chromatin architecture. Methylation of histone H3 at lysine 9 (H3K9) has emerged as an important player in the formation of heterochromatin, chromatin condensation, and transcriptional repression. Here, we have characterized a previously undescribed member of the histone H3K9 methyltransferase family named CLLD8 (or SETDB2 or KMT1F). This protein contributes to the trimethylation of both interspersed repetitive elements and centromere-associated repeats and participates in the recruitment of heterochromatin protein 1 to centromeres. Consistently, depletion in CLLD8/KMT1F coincides with a loss of CENP proteins and delayed mitosis, suggesting that this protein participates in chromosome condensation and segregation. Altogether, our results provide evidence that CLLD8/KMT1F is recruited to heterochromatin regions and contributes in vivo to the deposition of trimethyl marks in concert with SUV39H1/KMT1A.