"We've now restored full services," RIM's co-CEO Mike Lazaridis told reporters.
Some BlackBerry users may still see e-mails coming in slowly as the system recovers, he said.
The major outage frustrated customers on nearly every continent who were unable to send and receive e-mails and text messages this week. It also comes at a bad time for RIM, which is facing increased competition from Android and Apple smartphones.
The iPhone 4S is set to be released on Friday, and social media posts suggest some BlackBerry users may switch to other phones in part because of the prolonged break in services.
The outage started on Monday in Europe and spread to North America, Asia, Africa, the Middle East and South America over the course of the next two days. A failure at one of the company's messaging servers in Europe, along with the subsequent failure of its backup system, led to a ripple effect that reportedly caused problems for millions of BlackBerry owners.
Executives on Thursday did not answer questions about how many people were impacted by the four-day service outage, but they did say this breakdown was the largest in the company's history.
"We've worked 12 yrs since the launch of BlackBerry to win the trust of our 70 million BlackBerry subscribers and we're going to fully commit to win that trust back -- 100%," Lazaridis said during the press conference.
This is not the first time RIM has faced a major service outage.
"I have been an analyst for 25 years and have watched RIM wrestle with this same outage problem time after time. Every few years we get pinched by yet another major problem," tech analyst Jeff Kagan said in a statement.
This outage, however, comes at a particularly unfortunate time for RIM, since it faces increasing competition in the smart phone market, Kagan says.
BlackBerry users, many of whom use the devices primarily for business purposes, took to the Web to vent their anger about the outage. Twitter and other messaging platforms have been full of complaints since the outage began almost four days ago.