Marcelinas Siksnis finished a gymnasium in Siauliai in 1893. Then he graduated from the Mathematics Department of Moscow State University in 1897.
During 1899-1915 Marcelinas Siksnis taught at a Real Gymnasium in Riga. During the First World War (1915-1918), he taught at evacuated Lithuanian Gymnasiums in Voronezh.
In 1918-1939 Marcelinas Siksnis was a teacher and the principal during 1922-1939 at the Vilnius Vytautas Magnus Gymnasium. He played in the first Lithuanian amateur performances and was their director.
Marcelinas Siksnis published in Lithuanian periodicals since 1895 and translated poetry from Russian and Armenian as well. He wrote the tragedy "Pilenai Knyaz" which was staged in Riga in 1905 and in other places. He also written dramas "Wings" (1907) and "Fate's Punishment" (1911). He wrote several textbooks on algebra and geometry, which were taught in all schools of Lithuania before the Second World War.
Marcelinas Siksnis died on August 15,1970 in Vilnius, Lithuania.