The decree places the charismatic priest, a staunch anti-communist who laced his sermons with political messages backing the Solidarity trade union movement of future president Lech Walesa.
Three Polish secret service officers abducted Father Popieluszko in October 1984 after he celebrated his last mass in Bydgoszcz, central Poland.
They tortured him to death and then threw his body into the River Vistula, some 120 kilometres (70 miles) north of Warsaw.
His beatification process began in May 2001, and last year Benedict authorised a speedier procedure.
Because the murdered priest is considered a martyr, Popieluszko's beatification dossier did not require evidence of a miracle.
"Solidarity was alive because Father Popieluszko gave his life," Walesa said at a Rome screening of a documentary on Popieluszko.
"When the state cannot speak, the (Catholic) Church does. Without the symbiosis with the Church, Poland would have been wiped off the face of the earth," Walesa said.
The Nobel Peace laureate also said that he and Popieluszko felt the fact the pope at the time was Polish presented "an opportunity for Poland and other countries to make a break with communism."
Source: AFP Global Edition