In this paper an indicator for technical analysis based on fuzzy logic is proposed, which unlike traditional technical indicators, is not a totally objective mathematical model, but incorporates subjective investor features such as the risk tendency. The fuzzy logic approach allows representing in a more "human" way the decision making reasoning that a non-expert investor would have in a real market. Such an indicator takes as input, general market information like profitability and volatility of the stock prices, while the outputs are the buy and sell signals. In addition to present the detailed formulation of the indicator, in this paper a validation for the same is presented, which makes use of a multi-agent based simulation platform within which the behavior and profits obtained by agents that used traditional technical indicators such as MA, RSI and MACD, are compared against those obtained by agents that use the fuzzy indicator for the decision making process.