Lajpat Rai went to England in 1908 for the second time, delivered lectures to Indian students and returned to India in 1909. In 1913 he visited Japan, England and the United States on a lecture tour, and returned to India in 1920. During his stay abroad he is believed to have supported, the Ghadar Party's programme. He also established the Indian Home Rule League in the United States on October 15, 1916.

He resumed his political activities on his return to India in 1920. He attended the Calcutta and Nagpur sessions of the Congress in 1920 and also presided over the All India Student's Conference at Nagpur (1920). He was arrested in 1921 while presiding over the Punjab Provincial Political Conference. During his long stay abroad, Lajpat Rai saw India's struggle in a wider perspective against world movements and began to realise how India could win support from other countries. It was this which inspired him to write his major works: 'Young India', 'England's Debt to India', 'The Political Future of India' and 'Unhappy India'. In collaboration with Hardikar, he remained in close touch with British Labour and Irish organisation He was thinking at one time of writing a book on the application of Bolshevism to Indian conditions. Lajpat Rai worked passionately for the freedom of India and believed that without no improvement in economic and social conditions was possible. About student's participation in the freedom movement, he once said, "I am not one of those who believe that the students, particularly University students, ought not to meddle in politics. I think it is a most stupid theory". On his return in 1920 Lajpat Rai was shocked that British repression was even more ruthless than before. He reacted sharply to the Jallianwalla Bagh Massacre

After the advent of Gandhi, Lajpat Rai found a different world of politics, not really much to his liking, especially when he was called upon to preside over the Special Congress Session in Calcutta in 1920. Gandhi's politics looked to him as that of a visionary. Lajpat Rai was not enthusiastic about the Non-Cooperation Movement and predicted its failure; civil disobedience meant to him merely passive resistance which could never be effective in the conditions then prevailing. But like many others who had opposed Gandhi at the Calcutta session, he agreed with Gandhi at the Nagpur Congress Session (1920) and accepted non-violent noncooperation as an instrument of fight.

In 1921 Lajpat Rai presided over the Punjab Provincial Political Conference and was arrested. After his release and the withdrawal of the Non-Cooperation Movement, Lajpat Rai joined the Swarajya Party founded by C. R. Das and Motilal Nehru. On October 30, 1928, Lajpat Rai led a procession at Lahore for the boycott of the Simon Commission and received baton blows on the head and the chest from an English officer. Eighteen days, after this brutal assault he died of his injuries.

Lajpat Rai had a cosmopolitan outlook and was a staunch fighter against imperialism everywhere. He recognised the right of all the countries in Western Asia to freedom. He sympathised with the sufferings of Indians in South Africa. He had a high sense of national self-respect. He took Miss Mayo to task for her book, 'Mother India' to which he replied by his 'Unhappy India'. It was a powerful and a scathing refutation of Miss Mayo's scurrilous attacks on Indian society. Lajpat Rai was a prolific writer. He was deeply interested in journalism and founded an Urdu daily, the Bande Mataram and an English weekly, the People.

Lajpat Rai was called 'Sher-i-Punjab' (Lion of the Punjab). Although he may have been wanting in the charms of Gokhale and the sheer magnetic power of Gandhiji, his integrity, sacrifice and persuasive power gave a special dignity to his carriage.