He had complete command on Biblical Greek, Hebrew, Aramaic, Latin, Arabic, English and Urdu languages. He was knowledgeable about Biblical archeology and established a Bible museum at the Faith Theological Seminary, Gujranwala, Pakistan. Writing for Christian News International (CNI), Rev. Shahbaz Bhatti, entitled his article about him a "K.L. Nasir : A Man who did not compromise his faith". He served as a pastor in various villages in the Punjab as well as in the tribal area of Kohat India (now in Pakistan). He was appointed a professor at Gujranwala Theological Seminary in 1947 and its principal in 1958. As a convention speaker he attracted thousands to hear him expound and explain the Word of God. Being a gifted debater and articulate speaker he started expressing his view publicly right from his student life. In February 1941 he spoke powerfully against the "Christian Personal Laws" introduced by the Colonial British Rulers.
Dr. Kundan Lal Nasir was the founder-editor of Kalam-e Haq (کلامِ حق )(monthly magazine). The first issue of this magazine was published in January 1966. It was published regularly until 1994, however no issues appeared from August 1994 to May 1995. Its publication resumed in June 1995 under the administration of Faith Theological Seminary, Gujranwala, and Synod of the United Presbyterian Church of Pakistan. After the death of Dr. KL Nasir its editorial responsiblities were shouldered by his late son Rt. Rev. Dr. Major Timotheus Nasir.
Following is only a partial list of Dr. KL Nasir's books:
1. Sadaqat-e Bible (صداقتِ بائبل)
2. Tasdeeq-ul kitab (تصدیق الکِتاب )
3. Ilmul wa'az (علم الوعظ )
4. Ilm-e Illahi kay masail ( علمِ الٰہی کے مسائل )
5. Izhar ul haq ( اظہارالحق )
6. Ehd-e ateeq ki kitaboon ka dibacha (عہدِعتیق کی کِتابوں کا دیباچہ)
7. Bible muqadas aur asar-e qadeema (بائبل مقدس اور آثارِقدیمہ)
8. Bible Atlas o tarekh -e Bible (بائبل ایٹلس و تاریخِ بائبل)
9. Kaleedul kalam (کلید الکلام)
10. Umul kitab (اُم الکتاب)
11. Anbiya-e Qadeem (انبیاءقدیم)
12. Haqiqat-e Mirza baqalam khud (حقیقتِ مرزا بقلم خود )
13. Kashful Aqaid (کشف العقائد)