We determined the complete mitochondrial genome (mitogenome) of the Japanese Oak Silkmoth, Antheraea yamamai (Lepidoptera: Saturniidae) from two overlapping fragments and subsequent shotgun sequencing. The 15,601-bp long A. yamamai mitogenome contains gene arrangement and content identical to the most common arrangement found in lepidopteran insects. Most individual A. yamamai mitochondrial (mt) genes were well within the range found in the respective genes of other insects, except for small ribosomal RNA (1,037 bp). The 336-bp A+T-rich region is relatively smaller than that of other lepidopteran insects. The region is interesting in that it contains tRNA-like structures as found in the A+T-rich regions of other insect mitogenomes. The start codon of A. yamamai COI gene is unusual in that no typical one (ATN) is available. Three of the 13 protein-coding genes have incomplete termination codon T or TA. All tRNA formed stable stem-and-loop structure, except for tRNASer(AGN), the DHU arm of which formed a simple loop as seen in many other metazoan mt tRNASer(AGN).