The new law imposes hefty fines and long prison terms for cyber bullies and fake news dealers.
The new law spells out harsh punishment to cybercriminals and the process of seeking reparation by victims of cybercrime.
Former Law Society of Kenya chief executive Apollo Mboya said the context of "false information" will give the authorities a free opportunity to gag the media. The law also targets those who alter information through Photoshop.
"The Act also deals with computer forgery, computer fraud, cyber harassment, publication of false information, cybersquatting, identity theft and impersonation, phishing, interception of electronic messages or money transfers, willful misdirection of electronic messages and fraudulent use of electronic data among other cyber crimes", said a statement on the government website.
Those who spread child pornography are liable for a fine of up to $200,000 and a 25-year jail sentence.
The president signed the Bill despite opposition from the global media freedom watchdog, Committee to Protect Journalists (CPJ) which had called on Kenyatta not to sign the Bill because it will stifle press freedom.
The clause says if a person "intentionally publishes false, misleading or fictitious data or misinforms with intent that the data shall be considered or acted upon as authentic", they can be fined up to 5 000 000 shilling (nearly R620 000) or imprisoned for up to two years.
Uhuru also assented to the Public Trustee (Amendment) Bill, 2018, which changes various provisions of the Public Trustee Act for conformity with the Constitution.
Present during the signing at State House, Nairobi, were Deputy President William Ruto, Interior Cabinet Secretary Fred Matiang'i, National Assembly Majority Leader Aden Duale, Attorney General Paul Kihara Kariuki and Solicitor General Kennedy Ogeto.