The papal decree issued Thursday also broadened the definition of crimes against minors to include child prostitution, sexual acts with children and the creation or possession of child pornography.
Hundreds of people live and work in the Vatican city-state.
Francis also increased cooperation with other states on money-laundering and terrorism, reforms begun under his predecessor Benedict XVI, to get the Vatican on to an international financial-transparency "white list".
The new legislation also increases criminal liability for employees of the Vatican curia or government, which has been hit by a series of scandals.
Stealing documents from the Holy See will now be punishable with prison sentences of up to eight years.
The new laws were issued by Francis as "moto proprio", meaning they were his own initiative.
The Argentine pontiff is determined to wish to root corruption and malpractice in the Vatican government and its financial institutions, which have long been beset by money-laundering allegations.
The Vatican was hit by one of the worst security breaches in its history last year when Benedict's butler Paolo Gabriele leaked to Italian media hundreds of his private letters.
The leaked papal documents laid bare venomous power struggles and corruption within the curia, in what was known as the "Vatileaks" scandal.
Gabriele was jailed for the leaks but was released after Benedict pardoned him.