Shirakawa joined the Bank of Japan in 1972. His varied assignments at the bank included a period as General Manager at the Ōita branch. For a time, he was General Manager for the Americas at the bank's office in New York City.
Shirakawa joined the faculty of the graduate school of public policy at Kyoto University in 2006. He returned to BOJ in 2008.
His nomination to be Governor of the Bank was approved on April 9, 2008. Masaaki ranks 6th on the world's most powerful by Newsweek along with economic triumvirs Ben Bernanke (4th) and Jean-Claude Trichet (5th).
In 2011 he was included in the 50 Most Influential ranking of Bloomberg Markets Magazine. He is a member in the Group of Thirty.
In 2013 he accepted a professor post at Aoyama Gakuin University.