Ashwini Kumar Dutta initially began his career in 1878 as a teacher at the Krishnanagar Collegiate School. Later he joined the Chatra Nandalal Institution in Serampore and was appointed as the Headmaster of the institution. Dutta was called to the Bar at Barisal in the year 1880. He developed a productive practice and spent most of his earnings on philanthropic activities. Following the suggestion of the Magistrate of Barisal, Ramesh Chandra Dutta, Ashwini Dutta founded the Brojomohun School on 27 June 1884 and dedicated to his father. He was designated as a delegate to the second session of Indian National Congress Party that was conducted in the year 1886 at Calcutta (now Kolkata).
In 1887, Ashwini Kumar Dutta took the initiative to set up the District Board in Barisal. Dutta also established the Bakarganj Hitaishini Sabha as well as a girls' school in that year. In the same year he attended the third session of Indian National Congress held in Madras (now Chennai) and discussed about the requirement of reforms in the Legislative Council. In the year 1888, Dutta was appointed as the Vice Chairman of Barisal Municipality. Later in 1889, he constructed the Brojomohun College, which was a second grade college. Ashwini Kumar acted as the Honorary Lecturer of English at the college for around 25 years. He became the Chairman of Barisal Municipality in 1897. In the next year Ashwini Kumar Dutta was chosen amongst the committee that was enabled to form up a constitution of the Indian National Congress. He was drawn towards the Swadeshi movement during the Partition of Bengal.
Ashwini Kumar Dutta established the Swadesh Bandhab Samiti in order to encourage the consumption of native products and boycott European goods. The British Indian Government of India of the newly formed Eastern Bengal and Assam banned the Swadesh Bandhab Samiti in the year 1908. He was deported to the United Provinces where Dutta was imprisoned at the Lucknow jail. After Ashwini Kumar Dutta was released in the year 1910, he focused on managing the Brojomohun School and Brojomohun College. Later in the year 1912, Dutta was compelled to surrender the management of the school and the college to 2 distinct trustee councils. Ashwini Kumar attended the Bombay session of the Indian National Congress held in 1918.
Ashwini Kumar Dutta also undertook relief work after the cyclone in Barisal in 1919. At the Calcutta session of the Indian National Congress Party in the year 1921, he supported the non violent Non Cooperation Movement. Mohandas Gandhi, popularly known as Mahatma Gandhi, went in Barisal in the same year to respect the great leader. Ashwini Kumar Dutta also supported the workers of Assam Bengal Railway and Steamer Company who started a strike as a protest against the hostilities and violence on the workers of tea plantations of Assam in the year 1922.
Ashwini Kumar Dutta also wrote several books on philosophy, religion and patriotism in Bengali language. Some of his most well known books include, Bharatgeeti, Atmapratistha, Bhaktiyoga, Durgotsavtattva, Prem and Karmayoga. Ashwini Kumar Dutta died on 7 November 1923 at the age of 67 years.