Born in Suvalkija to a family of Lithuanian farmers, Mašiotas attended Marijampolė Gymnasium and studied mathematics at Moscow University.

He held this job until World War I forced him to evacuate to Voronezh where he became director of the Lithuanian girls' and boys' gymnasiums.

He returned to Lithuania in 1918 and started working on organizing the education system in the newly independent country.

He translated such children's classics as Maya the Bee by Waldemar Bonsels and Emil and the Detectives by Erich Kästner.

[3] Mašiotas was born on 19 December 1863 in Pūstelninkai [lt] near Kudirkos Naumiestis which was then part of the Russian Empire.

[5] He received a special government stipend for Lithuanian students (360 rubles annually) and enrolled into the Faculty of Physics and Mathematics at Moscow University.

He frequently collaborated with Marcelinas Šikšnys [lt], another Lithuanian math teacher at the Riga Gymnasium.

[7] In 1905, Mašiotas became a member of the 20-member committee tasked with organizing the Lithuanian Scientific Society which was officially established in April 1907.

[7] In summer 1915, as German Army approached Riga, Mašiotas evacuated to Moscow and then Voronezh where he became director of the Lithuanian girls' and boys' gymnasiums established by Martynas Yčas.

Due to political disagreements, the post of vice-minister was abolished in 1923 and Mašiotas was given the job as the director of the Vytautas the Great Gymnasium in Klaipėda [lt].

There are two versions of his retirement – due to disagreements with Klaipėda governor Antanas Merkys[5] or for health reasons (cheek neuralgia that would get so bad that he could not speak).

His daughter bibliographer Marija Mašiotaitė-Urbšienė [lt] and her husband Juozas Urbšys were arrested and deported to Siberia by the Soviets.

His wake was held at the Vytautas the Great War Museum; his funeral was a large public event attended by numerous government officials and writers.

In 1894, Mašiotas published an article in Varpas in which he outlined the basic requirements for children's texts – works should have aesthetic, educational, and moral value as well as be written in correct language.

[16] His later works and translations focused on educational value (e.g. teaching children about natural phenomena) as opposed to rousing child's creativity or imagination.

His travel books idealize Lithuania's nature but also include geographical, historical, ethnographic information.

[18] They were aimed at school students in hopes of spurring their interest in their native country and encouraging them to launch their own local studies.

[12] Mašiotas translated various authors, including Daniel Defoe, James Oliver Curwood, Erich Kästner, Hugh Lofting, Karin Michaëlis, Ferenc Molnár, Ernest Thompson Seton, H. G. Wells, Ernst Wichert, and many others.

[13] Mašiotas also published several popular science books for children, including Conversations about Sky and Earth (Pasikalbėjimai apie dangų ir žemę in 1901), How People Took Over the World (Kaip žmogus žemėje įsigalėjo in 1919).

Albinas Degutis compiled and published Mašiotas' bibliography (1990) and a collection of his articles, letters, and memoirs about him (2013).

In 2004, several wood carvers created sculptures for the Fairy Tale Park inspired by Mašiotas that was established around the house.

[19] In 1983, the 120th birth anniversary of Mašiotas, Vilnius University organized an academic seminar on children's literature in Lithuania.

It is held in December by the Lithuanian section of the International Board on Books for Young People (IBBY) and the Martynas Mažvydas National Library of Lithuania.

[20] In 2012, IBBY renamed its annual (since 1993) award for the best Lithuanian book for children and adolescents in honor of Mašiotas.