The purpose of this study was to develop a measure for self‐monitoring and self‐regulation of momentary mood states. The Two‐Dimensional Mood Scale (TDMS), consisting of eight words selected on the basis of pleasure and arousal, was created as an efficient measure of self‐monitoring. In Study 1, the validity and reliability of the TDMS were examined by administering the measure to 904 university students. Structural equation modeling revealed that mood states were constructed of two components, arousal and pleasure, and factor analysis found two factors, vitality and stability. In Study 2, differences between two mood manipulations, activation (exercise) and relaxation techniques were examined in 224 university students. The results showed that exercise induced higher vitality ( η P 2 = .62 , η G 2 = .28 ) but no change in stability ( η p 2 < .01 , η G 2 < .01 ), while relaxation resulted in an increase in stability ( η p 2 = .43 , η G 2 = .11 ) but no change in vitality ( η P 2 = .04 , η G 2 = .01 ). The TDMS can be combined with various mood manipulations to enable individuals to self‐regulate and alter negative psychological states.