This study used a sample of 314 British athletes (170 male, 144 female) to examine whether social-contextual and personal motivation variables proposed by self-determination theory (Deci & Ryan, 2002) can predict reported levels of sportspersonship and antisocial moral attitudes in sport. Structural equation modeling analysis showed that perceptions of coach autonomy support were positive predictors of athletes' satisfaction of their psychological needs for competence, relatedness, and autonomy. In turn, the three needs were positive predictors of autonomous motivation. Autonomous motivation positively predicted sportspersonship and negatively predicted antisocial moral attitudes in sport. The opposite pattern of results was observed between controlled motivation and the sportspersonship and antisocial moral attitudes variables. The findings emphasize the importance of autonomy supportive environments, psychological need satisfaction, and autonomous motivation for fostering sportspersonship in sport.