The all-in-one app is a daily necessity for most Chinese, bringing together messaging, social media, mobile payment, games, news and other services.
"WeChat's worldwide monthly active users have surpassed the critical one billion mark," CEO Pony Ma said Monday on the sidelines of China's parliamentary session underway in Beijing.
"In the future we hope to use technological innovation to push forward the next developmental step of reform and opening," Ma said.
He was referring to China's economic liberalisation policy that has fuelled four decades of breakneck economic growth.
Although Ma said WeChat's monthly active users had crossed the one billion thresholds, a company spokesman told AFP he was referring to its total number of accounts.
Still, the one billion figure indicates the huge user base which Tencent has built up both inside and outside China for its all-in-one app.
It compares with 2.1 billion monthly active users on Facebook and 1.5 billion on its messaging app WhatsApp.
The popularity of WeChat -- and profits from its addictive mobile games -- have pushed Tencent's earnings and share price sharply upwards.
The company surpassed Facebook in market value last year and the 47-year-old Ma has rocketed to near the apex of China's rich list.
He is the wealthiest delegate to the parliamentary session, according to Shanghai-based luxury magazine publisher Hurun Report, which estimated his fortune at $47 billion (roughly Rs. 3.05 lakh crores).