Moriyama started helping out with in-between animation when he was a student at Kanto Daiichi High School.
After graduating from high school, he joined Studio Musashi, which was recruiting staff through newspaper ads.
At NeoMedia, he worked on Invincible Robo Trider G7 for Sunrise, Doraemon for Shin-Ei Animation, and Belle and Sebastian for Visual 80.
Yuji Moriyama is credited with character design and animation director for the Project A-Ko series.
Some of his many pennames include Motoyama Yūji (もとやまゆうじ), Saihō Jōdo (西宝 壌土), Kazama Kotarō (風間 小太郎), Sunakawa Norihiro (砂川 則博), MONTAN, Shibakano Wataya (芝跨野 渡也), Shibamata Tōya (柴又 十哉), Aran Sumishi (阿藍 隅史), Nekobu Nachiko (猫部 那智子), and Gyoden Tadao (魚田 尹夫).