As an undergraduate, he published two papers in the Japanese Journal of Mathematics and the Proceedings of the Imperial Academy of Tokyo.

During his time in Europe, he met with top mathematicians such as Claude Chevalley, Henri Cartan, and others.

He managed to solve a question of Artin on generalizing the principal ideal theorem and this was published in 1939.

Iyanaga did publish many papers which arose through several courses such as algebraic topology, functional analysis, and geometry, which he taught.

Towards the end of the war, many Japanese cities were bombarded and he had to find refuge in the countryside.

He was busy in editing textbooks from primary and secondary schools and he continued to give courses and organise seminars.