The ‘low-volatility anomaly’ is the counter-intuitive observation that portfolios of low-volatility stocks tend to yield higher risk-adjusted returns than portfolios of high-volatility stocks. In this article, we investigate if the anomaly holds, not only for portfolios consisting of individual low-volatility stocks, but for portfolios that have been optimized to minimize aggregate volatility. We exploit patterns in historical price fluctuations to identify optimized portfolios whose aggregate volatility is expected to remain low. These portfolios are evaluated by comparing them against the performance of market capitalization and low-volatility quintile benchmarks out-of-sample. The results reveal that, as well as outperforming the market, both in terms of returns and risk, optimized low-volatility strategies also outperform the S&P Low-Volatility Index. These findings provide further support for a low-volatility effect, and imply that the root of the anomaly may lie with a failure to exploit diversification opportunities.