Was born Tej Ram on 2 June 1894 at the village of Adiala in Rawalpindi district, now in Pakistan. His father's name was Bhalakar Singh. At the age of three, Tej Ram was sent to the village gurdwara to learn to read and write Gurmukhi and later to the mosque to learn Urdu and Persian. While still a small boy, he received initiatory rites at the hands of Baba Sir Khem Singh Bedi and was converted to Sikhism with the name of Teja Singh. His early life was very hard and full of adventure. Since his father could not afford to send him to a regular school, he absconded from home in search of education. He managed to attend schools in Rawalpindi and thereafter in Sargodha and enter the Khalsa College at Amritsar after passing his matriculation examination.

Teja Singh had a sensitive nature. The babbling brooks of Pothohar and the stories of the Gurus and heroes he had heard as child shaped his imagination. In his seventh form, he wrote in English a treatise on painting and depicted in drama the noble and heroic martyrdom of the sons of Guru Gobind Singh. He painted pictures and although he had to work to pay his way through college, he had engaged a musician from a neighbouring village to come daily to his hostel to play the sitar for him.

After passing the intermediate examination from Khalsa College, Teja Singh returned to Rawalpindi to join the Gordon College which had afforded him a fee concession. He took his master's degree in English literature in 1916. In March 1919, he got an appointment at the Khalsa College at Amritsar where first he taught history and then for a quarter of a century English literature. Those were the days of much political activity in the Punjab of which Amritsar was an important centre. Teja Singh was among the 13 Sikh professors of Khalsa College who resigned as a protest against government's control in the management of the institution. This gave rise to a widespread agitation and the government was forced to replace all 11 official members of the Khalsa College Managing Committee by "non-official" Sikhs. Teja Singh was also connected with the Sikhs' long-drawn struggle in the twenties for the release of their holy places from the control of an effete and corrupt priestly order. In 1923, he was arrested during this campaign and served more than one year in jail. On his release in 1925 for reasons of health, he returned to Khalsa College and his old profession of teaching. But he retained his contact with public causes through his writings and lectures. In 1939, he undertook a lecture tour of Malaya and delivered nearly 300 speeches in two months' time.

A gracious and kindly figure radiating warmth and friendliness, Teja Singh presided over the cultural and literary activity in the Punjab for three decades. Punjabi letters and Sikh history and philosophy were his special fields of study. In the former he exercised pontifical influence and initiated new values and standards. With his vast background in oriental learning combined with a deep study of Western literature, he was an ideal critic and arbiter of literary excellence. His writings helped to fix the form and structure of Punjabi idiom. He encouraged and introduced to readers many young writers and it was accepted custom for all new practitioners to first show their work to him.

As a scholar of Sikh religion, he wrote copiously and authoritatively on the subject. He was for many years the interpreter and expositor of Sikhism to the outside world through his articles in English. Such writings of his were collected in book form and published under the titles Sikhism : Its Ideals and Institutions (1938) and Essays in Sikhism (1944). He wrote in collaboration with Dr Ganda Singh A Short History of the Sikhs (1950). Some of his renderings of the holy texts such as japu, Ass ki Var and Sukhmani had established themselves as classics. The Sabadarth, an annotated edition of the Guru Granth Sahib, sponsored by the Gur Sevak Sabha, which was completed in five years (1936-41), was primarily the work of Teja Singh. Teja Singh also compiled an English-Punjabi dictionary. One of his ambitions was to render the entire Guru Granth Sahib into English. The portion he had completed during his lifetime was published by the Punjabi University in 1985 under the title The Holy Granth (Sri Rag to Rag Majh).

In Punjabi literature Teja Singh is remembered primarily as an essayist. The first collection of his essays in Punjabi was published in 1941 under the title Navian Sochian, followed by Sahij Subha in 1942 and Sahit Darshan in 1951. His autobiography, Arsi (Finger-Glass of Memory), a model of chaste and crisp Punjabi prose, was published in 1952. A scholarly work in Punjabi was Sri Guru Granth Sahib vich Shabadaritik Lagan Matran de Gujhe Bhed ( Subtle Distinctions of Wordending Vowel Symbols in the Sri Guru Granth Sahib).

In 1945, Teja Singh took over as Principal at the Khalsa College at Bombay. He stayed at this post for about three years and. then returned to Punjab as Secretary of the Publications Bureau of the Punjab University. In January 1949 he was appointed Principal of Mohindra College, Patiala. At Patiala, he also held additional charge for a time as Secretary and Director of the newly established Punjabi Department. He retired from the service of the PEPSU government in 1951.

Teja Singh died after a stroke at Amritsar on 10 January 1958. He is remembered as a great man of letters who combined with deep learning a rare personal charm and kindliness.