In fish, maternal RNAs that are incorporated into the developing oocytes include ribosomal RNA (rRNA), transfer (tRNA), and messenger RNA (mRNA), the two former of which are components of the protein translation machinery and the latter of which is used as a blueprint to synthesize proteins, as well as microRNA (miRNA) and other non-coding RNA (ncRNA), which are not used to make proteins, but instead play regulatory roles (Pauli et al., 2011; Pelegri, 2003). These factors are produced by the mother based on her genome and deposited into the developing egg at a very early stage of oogenesis. This article will focus on the localization, regulation, and function of coding and non-coding RNAs. Much of the knowledge we have on maternal RNAs in fish have been obtained from teleost species (ray-finned fishes that make up 96% of all fishes) including zebrafish (Danio rerio), medaka (Oryzias latipes), and to a lesser extent goldfish (Carassius auratus). These are all small aquarium fishes used as experimental laboratory models due to their ease of reproduction in captivity and abundant egg production that are easily handled in culture. Findings were also obtained from wild and farmed fish species, such as rainbow trout, salmon, and tilapia just to name a few. The major differences between fish species and other vertebrates are that their eggs are fertilized and develop externally and can be produced year-round. In this article, we will introduce the localization, regulatory mechanisms and function of some protein-coding and non-coding transcripts that have previously been investigated in fish eggs.