In 1905—1906 Sierada served in the Russian army in Manchuria and was also mobilized during World War I.
He graduated from a veterinary school in Warsaw in 1903 and worked as veterinarian in the Minsk Governorate in 1907—1911. At the same time he was a teacher at an agricultural college in Marijna Horka.
Jan Sierada was active member of the Belarusian Socialist Assembly. In 1917 he was chairman of the First All-Belarusian Congress. In 1918 he was elected president of the Belarusian Democratic Republic.
In the 1920s Sierada worked on different positions in Agriculture Ministry of the Belarusian SSR, was also teacher at several colleges and published several works on agriculture.
On July 4, 1930 Sierada was arrested by the NKVD as part of the so-called Case of the Union of Liberation of Belarus. In April 1931 he was sentenced to 5 years exile in Yaroslavl, Russia. After return, he was again sentenced in 1941 to 10 years of concentration camps. He was set free on November 19, 1943, from Kraslag camp chain (Krasnoyarsk Krai) and his further fate is unknown.
He has been rehabilitated on his cases in 1988 and 1989.
- Як трэба каваць коні. Мн., 1926;
- Вэтэрынарыя і зоагігіена. Кн. 1-2. Мн., 1927–1928;
- Пабудова сіласаў у калгасах і саўгасах. Мн., 1930.
- Маракоў Л.У. Рэпрэсаваныя літаратары, навукоўцы, работнікі асветы, грамадскія і культурныя дзеячы Беларусі, 1794-1991. Энц. даведнік. У 10 т. Т.2. —Мн:, 2003. ISBN 985-6374-04-9