Born in Vienne, Isère, Viannet began training as a controller for the Postes, Télégraphes et Téléphones (PTT).

He completed his training, and his compulsory military service, then returned to work for the PTT in Lyon.

[1][2] In 1982, Viannet began working full-time in the CGT office, as director of La Vie Ouvrière, the federation's weekly newspaper.

Within the party, he was regarded as an orthodox figure, whereas the federation's general secretary, Henri Krasucki, was seen to be becoming more moderate, and distancing himself from the PCF.

[1][2] Under Viannet's leadership, membership of the CGT increased, and it placed first in the labour court election of 1997.