Joint investigations by the Malta Gaming Authority and the Executive Police determined the company was processing payments to and from players as part of a service which was not authorised.
Blackrock has now paid the fine after reaching a settlement with the MGA.
Silvio Schembri, Parliamentary Secretary in the Maltese Government, said: "This is proof our institutions work diligently, efficiently and effectively.
"It should be noted this is the highest fine ever issued by the Malta Gaming Authority, which proves the credibility and seriousness the authority operates with, to safeguard the reputation of the Maltese jurisdiction in this field.
"The gaming industry is an important element of our economy and we must continue to make sure our jurisdiction will continue to raise the bar and retain the title as the home for gaming excellence."
