Nguyễn Trọng Kiệm was born in 1933 in Hưng Yên province, into a poor family. In 1945, his family moved to Lào Cai province, on the border with China, to find work as manual labourers. As a child, Trọng Kiệm loved art and would draw on walls. These drawings were seen by artist Nguyễn Trọng Hợp, who happened to be working for the Việt Minh (League for the Independence of Vietnam) in the region. Trọng Hợp took him under his wing and enrolled him in school, so that he would learn reading and writing. From 1946-47, Trọng Kiệm worked for the Việt Minh as communicator around Cốc Lếu, in Lào Cai province. This involved swimming along the river so as to cross the border to a safe zone in China, while carrying documents in a bamboo tube. From 1948-49, he worked in Hà Giang province, making propaganda drawings for the resistance movement against the French.

In 1949, Nguyễn Trọng Hợp took Trọng Kiệm to meet Tô Ngọc Vân, in the hope that Trọng Kiệm would be accepted as an art student. Nguyễn Trọng Kiệm was admitted to study art in the Resistance School of Fine Arts in the hills of the Việt Bắc until 1954. During that period, his teachers included Trần Văn Cẩn, Nguyễn Văn Tỵ and Nguyễn Tư Nghiêm. Throughout his last year as a student, he made illustrations for a resistance newspaper. In 1955, Trọng Kiệm began teaching at the Hanoi Industrial Fine Art University, where he worked until his death in 1991. In addition to holding a teaching post, Trọng Kiệm was also respected as a successful artist. The majority of his paintings were in line with State-supported nationalistic themes. However, in his private time, he took risks in exploring subjects and styles beyond the officially acceptable boundaries of social realism and propaganda art.