Based on an integrated framework of the self-determination theory and the control-value theory of achievement emotions, the current study investigated the impact of basic psychological needs (BPN) satisfaction on two types of educational outcomes, i.e., academic achievement and positive emotions in second language (L2) acquisition. This study also explored whether academic self-concept (L2 self-concept in this case) would mediate the effects of BPN satisfaction on L2 achievement and emotions. A total of 391 Chinese undergraduates studying English as a foreign language were recruited for the present study. They completed measures on basic psychological needs satisfaction, L2 self-concept (English self-concept in this case), English achievement, and positive academic emotions (i.e., enjoyment, pride, and hope). After controlling for demographics, structural equation modeling indicated that BPN satisfaction was positively associated with positive emotions and this association was partially mediated by English self-concept. More importantly, English self-concept fully mediated the positive impact of basic psychological needs satisfaction on English achievement. Our findings acknowledged BPN satisfaction as a contributor to desirable learning outcomes and highlighted the important role of L2 self-concept in second language acquisition. Satisfying students’ basic psychological needs and particularly maximizing their L2 self-concept have significant pedagogical implications for second language education.