It is not known when Shen Youzhi was born. However, it is known that his father Shen Shuren (沈叔仁) was an army officer under Emperor Wen's brother Liu Yiji (劉義季) the Prince of Hengyang and was a cousin of the famed general Shen Qingzhi (沈慶之). Shen Shuren's household was not rich, and he grew up in poverty after apparently losing his father early in life. In 450, when Northern Wei forces made a major invasion into Liu Song territory, Shen Youzhi was conscripted, and he went to see the general Liu Zunkao (劉遵考) to request a sergeant position. Liu was not impressed by his appearance and refused his request, so he went to follow his distance uncle Shen Qingzhi. However, Shen Qingzhi did not initially make him an officer either, and he did not become an officer until 452, when he followed Shen Qingzhi in a campaign against the Xiyang Aborigines (西陽蠻, located in modern Huanggang, Hubei).