In this study, I present a comprehensive analysis of codon usage bias in 43 herpesviruses for which the whole genome has been sequenced. The values of the effective number of codons revealed that the majority of the herpesviruses did not have high codon bias, with the exceptions of only simplexviruses and some varicelloviruses. The results of correspondence analysis, a plot of ENC and GC content at the third position of the codon and analysis of preferred codons all revealed that the codon bias was mainly influenced by nucleotide composition. This suggests that mutation pressure is the main factor influencing codon usage bias in herpesviruses.