The mitochondrial salvage pathway supplies deoxyribonucleotide triphosphates for mitochondrial DNA synthesis. Its rate limiting enzymes are deoxyguanosine kinase (dGK) and thymidine kinase2. Mutations in these enzymes lead to several mitochondrial diseases in infants. Deoxyguanosine kinase3 (dGK3) is an isoform of dGK that was cloned from gestational day 8 mouse embryos. The objective of this study was to characterize the developmental expression of dGK3 in mouse embryos. Non-radioactive Northern blot and reverse transcription-polymerase chain reaction analyses were used. Expression analyses showed that the smaller sized transcript of dGK3 was expressed in embryos from gestational day 8 through day 17. Expression levels were uniform from gestational day 8 to 15 with the lowest expression on gestational day 17. Further analyses showed expression of the gene in multiple adult tissues indicating the dGK3 is not an embryonic isoform of dGK. This study is the first analysis of dGK3 expression during early development.