But while they will have to relay any concerns to the church authorities, they do not have to inform the police.
Until now, reporting suspicions has been a matter of individual conscience.
The new church law aims to hold the Catholic hierarchy accountable for failing to protect their flocks. It marks the latest effort by the Pope to address the sex abuse and cover-up scandal that has rocked the Catholic Church and his own papacy.
The law also allows victims, or those representing them, to report alleged clerical abuses directly to the Vatican, after procedures at diocesan level were discredited by multiple cover-ups.
In addition, clerics cannot order anyone who reports abuse to remain silent.
And the document provides protection for whistleblowers, who it says must not suffer “prejudice, retaliation or discrimination”.
Every diocese must set up a system through which claims of sexual abuse and cover-up can be reported confidentially by 1 June 2020.
Qualified lay experts will be called in to help with investigations, and victims will be told the outcome of an investigation if they request the information.
The Vatican has long argued that requiring clerics to report to the police could endanger the church in places where Catholics are a persecuted minority. But the law says that clerics should continue to follow local law when deciding to report alleged sexual abuse to civil authorities.
It has been suggested that a special fund be set up to pay for investigations.
The Pope summoned senior church leaders to a summit on sexual abuse in February
As well as introducing new rules, the document also defines crimes that should be reported.
These are: performing sexual acts with a minor or vulnerable person; forcing someone by “violence, threat or through abuse of authority, to perform or submit to sexual acts”; production, exhibition, possession or distribution of child abuse material, as well as inducing a minor or vulnerable person to participate in exhibiting porn.
Cover-ups that must be reported are defined as “actions or omissions intended to interfere with or avoid civil investigations or canonical investigations”.
Pope Francis’s edict has emerged three months after he summoned senior church leaders to Rome in February for a summit on sexual abuse.
The scandal has battered the Catholic Church’s reputation and has been a major challenge for Francis since his 2013 election.
Former US Cardinal Theodore McCarrick was defrocked in February after he was found guilty of sexual crimes against minors and adults.
Some dioceses have gone bankrupt after paying settlements to victims.
