His maternal grandmother was Hella Wuolijoki, the Estonian born writer and socialist activist.

In addition to Finnish, Tuomioja speaks Swedish, English, French, German and Estonian.

Tuomioja, like several other Finnish socialist politicians of today, took part in the illegal occupation of the Old Student House (Vanha ylioppilastalo) in Helsinki on 25 November 1968.

Despite his anti-war stance, Tuomioja did carry out his own mandatory military service and is a reservist staff sergeant.

His A Delicate Shade of Pink about his grandmother Hella Wuolijoki and her sister Salme Murrik won the Non-Fiction Finlandia Prize in 2006.