Fr de Assis Ribeiro was born on 26 July 1966 in Capitão Poço, State of Pará, Brazil. He entered the Salesian novitiate of São Carlos in 1986, professed perpetual vows on 7 September 1992 in Rome, where he studied theology at the Salesian Pontifical University, and was ordained priest on 17 June 1995 in Ourém, Brazil.
The various positions he held in the Salesian works of his Province include: Economer of the "Domingo Savio" and "Aleixo" houses of Manaus (1995-1996); Vicar of the Manaus Vocational Training Center (1997); Director of the "Sacramenta" house in Belém (1999-2005); Drector of the Salesian Mission, Economer and Parish Priest in Iauaretê, in the diocese of São Gabriel da Cachoeira (2006); Director (2006-2009) and parish priest (2006-2010) at the "Dom Bosco" house in Manaus; then parish priest in Manicoré (2010-2013). He is currently Vicar of the "Domingos Savio" house in Manaus.
For the BMA Province, he was in the Youth Ministry team (2004-2009); Delegate for the Missions (2006-2007) and Delegate for the Salesian Family (2007-2009). Since 2012, he has been Provincial Vicar, and since 2013 Delegate for Youth Ministry once again.