Between 1901 and the outbreak of World War I, he designed more than 130 private and public buildings in Riga, most of them in Art Nouveau style.

After graduation of local parish school he started to work under his uncle J. Brauns who was a known Latvian builder.

In 1894 Alksnis together with engineer J. Krūmiņš traveled to Siberia where they worked on the construction of Trans-Siberian Railway line around lake Baikal.

It gave rights to design buildings and to supervise construction works however he was not allowed to call himself architect or civil engineer.

The overwhelming majority of work by Jānis Alksnis is distinguished for its high artistic value and emotional expression, and a great deal of his buildings belong to the most beautiful houses in the centre of Riga.