Jammwal was born in Jammu, Jammu and Kashmir. He was one of three children born to an Indian Army officer, and lived in various parts of India (owing to his father's transferable job) and trained in Kalaripayattu in an ashram in Palakkad, Kerala since he was three years old, which was run by his mother. He traveled to many countries training with martial artists in various forms, some of which find their base in Kalaripayattu. After earning a degree in martial arts, Jammwal traveled to over 25 countries, where he performed in live action shows. He participated as a contestant in Gladrags in the year 2000 and has been living in Mumbai ever since. He was a model in Delhi since 1996, but after a dismal career in modelling, landed his debut role in Shakti, a Telugu film. He later landed his first role in a Bollywood movie in Nishikant Kamat's Force after one audition.