After obtaining a master's degree in biology, he entered the International Seminary of Saint Pius X at Fribourg in October 1969.

Lefebvre did not have a pontifical mandate for these consecrations, which was promised in exhausting negotiations, but always postponed or subjected to destabilizing conditions.

[2] On 1 July 1988 Cardinal Gantin issued a declaration stating that Lefebvre, bishop Antônio de Castro Mayer, de Mallerais, and the three other newly ordained bishops "have incurred ipso facto the excommunication latae sententiae reserved to the Apostolic See.

"[6] By a decree of 21 January 2009 (Protocol Number 126/2009), issued in response to a request which Bishop Fellay made on behalf of all four bishops whom Lefebvre had consecrated on 30 June 1988, the Prefect of the Congregation for Bishops, Cardinal Giovanni Battista Re, by the power expressly granted to him by Pope Benedict XVI, remitted the alleged automatic excommunication which they had thereby incurred, and expressed the wish that this would be followed speedily by full communion of the whole of the Society of Saint Pius X with the Church, thus bearing witness, by the proof of visible unity, to true loyalty and true recognition of the Pope's Magisterium and authority.

[8] On 28 September 2024, Tissier de Mallerais suffered a skull fracture and internal haemorrhage due to a trip and fall on stairs in the seminary in Écône.