The success of both oogenesis and early embryo development relies heavily on dynamic epigenetic regulation in which gene activity changes without affecting the underlying DNA sequence. Epigenetics works through two main mechanisms: DNA methylation and histone modifications. DNA methylation typically leads to gene silencing, while histone modifications can either activate or repress genes depending on the specific modification, histone type, and targeted amino acid residue. Histone modifications affect important DNA regulatory processes in which the histone core area as well as the N-terminal tails that extend from the core region are vulnerable to a variety of posttranslational modifications (PTMs), including methylation, citrullination (deimination), acetylation, phosphorylation, ubiquitination, SUMOylation, ribosylation, and lactylation. This review article focuses on what is known about changes in the histone modifications and how these modifications and their responsible enzymes operate throughout mammalian oocyte maturation and early embryo development, highlighting their crucial roles in these processes.