In recent years China's national oil companies (NOCs) have proactively ventured abroad to look for more fossil fuel supply. Despite the divided views on their foreign energy quest, previous studies tend to consider the Chinese government and its NOCs to be a monolithic organism, and explicitly or implicitly presuppose that the Chinese NOCs' foreign energy quest could enhance China's energy security. This is, however, an untested hypothesis. To fill the gap, this article assesses the impact of Chinese NOCs' foreign energy quest on the country's energy security. Findings show that the Chinese NOCs have made some progress in their foreign energy quest, which contributes to their coffers and reserves, but that does not mean that China's energy security is greatly enhanced; in particular, the diversity and reliability of China's foreign oil sources are questionable.