This study attempted to build a model of involvement in sports participantion and spectatorship, flow experience, and intentions in watching baseball games. It was hypothesized that the relationship between involvement and flow experience in base-ball spectators, in which mediators can influence baseball participation invovlement and spectators’ intentions in baseball. The study participants were drawn from the professional baseball games spectators in Kaosiung country and Taichung stadium, and the universities students in central Taiwan. Questionnaires included the measures of involvement in sport participatnts and spectatorship, flow experience, and inten-tions. Measurement of sports participation invovlement used the perceived importance, self-expression, and centrality to lifestyle in the affective aspect of recreation spe-cialization of three-dimension involvement scale. The measure of sports spectatorship involvement included the perceived importance and centrality to lifestyle with the so-cial-psychological aspect of the sport spectators’ involvement scale. Flow experience was measured with two-dimension of concentration on the task at hand and loss of self-consciousness in flow state scales. Intentions were measured with consumer be-havioral intentions scale. The scales’ Cronbach’s alpha was .94~.96. The results show that the more the spectators’ involvement is, the higher their flow experiences are. Fi-nally, it was suggested that sports spectators’ involvement and flow experience in baseball play important roles mediating the relationship between baseball participa-tion involvement and the intention of watching sports. In future research, we can at-tempt to examine the relationship between sports spectators’ involvement and flow experience in different sport events, to design a sport spectators flow experience scales, and to test a model examining the enduring involvement, situation involve-ment and flow experience in spectator sports.