He hailed from Pingling 平陵 (near modern Xi'an 西安, Shaanxi) and excelled in the examinations about the Confucian Classics, which allowed him being appointed court gentleman (lang 郞), which he had to leave soon because of some quarrels. The Chamberlain for Attendants (guanglu xun 光祿勳) helped him being appointed aide (cheng 丞) to the governor of Nanling 南陵, then guard commander (wei 尉) of the tomb mound Changling 長陵.
Recommended by Guo Pulong 郭樸龍, he was granted the title of Senior Grand Master of the Palace (taizhong dafu 太中大夫) and appointed governor (taishou 太守) of the commandery of Jiujiang 九江, then Henan 河南. In 10 BCE he was called back to the court to take over the office of Chamberlain for Dependencies (da honglu 大鴻臚).
In 7 BCE he was appointed metropolitan magistrate (jingzhao yin 京兆尹), two years later Censor-in-chief (yushi dafu 御史大夫). In 4 BCE he succeeded Ping Dang 平當 in the office of Counsellor-in-chief (chengxiang 丞相) and was concurrently given the title of Marquis of Xinfu 新甫侯.
Wang Jia was known as an honest and upright person who tried promoting the competent and fighting the corrupt officials. In 2 BCE remonstranted against the growing influence of Emperor Ai's 漢哀帝 (r. 7-1 BCE) minion Dong Xian 董賢, was therefore put into jail and died by refusing to eat. His territory was confiscated. In 4 CE Emperor Ping 漢平帝 (r. 1 BCE-5 CE) bestowed him the posthumous title of Marquis Zhong 忠侯 and invested his son Wang Chong 王崇 as Marquis of Xinfu.