The Tokyo-based nonprofit Council for Sports Ecosystem Promotion released a report highlighting the rapid expansion of the illegal cross-border sports betting market in recent years.

Drawing on data from international market research firms and licensed operators in jurisdictions where sports gambling is legal, the report follows the recent referral of two professional baseball players to prosecutors for allegedly betting through overseas platforms while in Japan.

According to the report, individuals in Japan wagered a total of ¥5.43 trillion on sports events held outside the country via overseas betting websites. An additional ¥1.02 trillion was placed on domestic sports, with professional baseball accounting for the largest share at ¥528.1 billion, followed by soccer at ¥333.4 billion, and basketball at ¥86.9 billion.

In stark contrast, Japan’s legal sports lotteries generated just ¥133.6 billion in sales during fiscal 2024, which ended in March—highlighting the vast scale of the illegal market.

Gambling is tightly regulated in Japan, with only specific government-approved activities such as horse and motorboat racing permitted. Residents found gambling on overseas online casinos, even if legal abroad, may face fines of up to ¥500,000 (about $3,400) or imprisonment of up to three years for repeat offenses.

A key driver behind the surge in illegal betting is the low public awareness that using overseas gambling sites is prohibited. The proliferation of Japanese-language gambling websites and social media advertisements targeting local users has further fueled the trend, which the council warns is becoming a serious social problem.

Local authorities are increasingly overwhelmed. In 2024, a record 279 people were arrested in connection with online betting—an increase of roughly 160% from the previous year.

Previously, such gambling occurred mainly in specialized establishments located in entertainment districts. Now, with the ubiquity of smartphones, users can easily gamble by purchasing points through bank transfers or credit cards, significantly increasing accessibility.

A March survey by the National Police Agency estimated that 3.37 million people in Japan have used online gambling sites, with 43.5% of respondents unaware that such activity is illegal under Japanese law.

Despite the growing issue, law enforcement struggles to tackle cases involving operators based overseas due to jurisdictional limitations.

To address the problem, the council intends to collaborate with international sports organizations to combat cross-border illegal betting. It also plans to ramp up public education campaigns aimed at safeguarding athletes and preserving the integrity of sports, amid concerns that Japan’s domestic preventive systems lag behind global standards.