The President assented his signature to the bill Tuesday, May 21, 2019.
However, the bill will only come into operation in January 2020, according to the President.
After about two decades of waiting, Parliament on Tuesday passed the Right to Information Bill (RTI) in March this year.
In a short remark to assent to the Act at the seat of government in Accra, Nana Addo said the implementation of the law will boost the country's good governance and the fight against corruption.
He said "Properly applied, it will enhance the quality of our governance in the country and provide the critical tool in the fight against corruption in the next financial year i.e January 2020."
He said he was "very happy that this law has finally been passed” after exhaustive parliamentary processes.
"I want to congratulate the 7th Parliament for its courage, sense of responsibility and commitment to good governance in passing this significant piece of legislation."
The New Patriotic Party (NPP) promised during the 2016 election campaign to pass the bill into law when voted to power.
The government has since being under pressure from civil society groups and the media to pass the bill into law after Vice President, Dr. Mahamudu Bawumia, promised in February 2017 that the bill was going to be passed within 100 days.
Some Members of Parliament contented with the passage of the RTI bill into law.
MP for Asokwa, K.T Hammond mounted strong opposition to the passage.
He said the bill will render the country ungovernable.
"It is a recipe for disaster. It is a recipe for bad governance... Ministers can't operate, governments cannot proceed effectively, governance cannot take place meaningfully," he stressed.
The bill was first drafted 22 years ago under the auspices of the Institute of Economic Affairs, IEA.
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The draft Executive Bill was subsequently reviewed in 2003, 2005 and 2007 but was never laid in Parliament until February 5, 2010.
It was subsequently withdrawn to review some clauses.
Since then, efforts by several advocacy groups to put pressure on the duty bearers to have the bill passed have also not yielded any positive results until now.