If energy security is defined as the availability of energy at all times in various forms, in sufficient quantities and at affordable prices, without unacceptable or irreversible impact on the economy and the environment, Japan is facing an energy security predicament. For a country that was already uneasy about energy security, the March 11, 2011 earthquake and tsunami, which caused a nuclear catastrophe in TEPCO's Fukushima Daiichi nuclear power plant, turned this unease into outright anxiety. With the temporary and/or permanent closure of many nuclear reactors Japan has had to replace lost power. Tokyo has had no choice but to secure additional fossil fuels, a strategy that has negatively affected Japan's economy due to rising fuel costs. The increase in Japan's fossil fuel consumption has also caused a significant increase in greenhouse gas emissions, and affected Tokyo's commitment to Kyoto targets. This paper analyzes the consequences of the 2011 nuclear disaster for Japan's energy security. Recognizing that Japan's future energy policy choices are constrained and path dependent, the paper outlines energy policy recommendations for Japan's government.