A blimp is introduced as a stable platform for remote-sensing instruments required for unmanned aerial observation and surveillance. For developing flight control systems of the blimp, a series of experiments has been conducted to identify its flight dynamics. The paper addresses the blimp configuration, the experimental set-up, the method for identifying its dynamics, and the results of the identification in comparison with analytical estimation. The experimental method employs constrained flight tests using the full-scale blimp, and the data reduction for the identification uses an extended least-squares method involving the gradient algorithm. The result suggests that analytical formulas for estimating the parameters including added mass effects and stability derivatives may yield values consistent with experimentally identified ones.