After being apprenticed to a shoemaker for a year, he quit to become the painter"s assistant.
He was first inspired to pursue an artistic career by the parish painter, who was teaching him to read and write. In 1859, the Vicar, Frans von Knorring, happened to see some of Jansson"s drawings and sent them to the Finnish Art Society with a letter of recommendation. As a result, he was given a scholarship to study at the Society"s drawing school in Turku, which was under the management of Robert Wilhelm Ekman.
Upon his arrival, Ekman arranged for lodging and provided the necessary art materials.
In 1862, he moved to Stockholm to continue his studies at the Royal Swedish Academy of Arts with Johan Fredrik Höckert. In 1867, he graduated and received a state scholarship to study at the Kunstakademie Düsseldorf under Benjamin Vautier.
This period was the most decisive in determining his style. He attended classes until 1872, between periods spent at home in Finström.
By this time, he had been diagnosed with tuberculosis and went to Rome, seeking a healthier climate.
Finding little relief, he travelled to various health resorts, including Davos and Merano, with no improvement. After a few months spent completing his affairs in Düsseldorf, he returned home for what would be the last time.
On his deathbed, he learned that he had been accepted as an associate member of the Imperial Academy of Arts.