Abstract: This study examined the relation of adolescents' ratings of the fulfillment of the intra-personal needs for autonomy, competence, and relatedness, as well as the balance between challenge and skill, with student engagement and achievement. Thus, this study brought together elements of two different bodies of literature—student engagement and flow—to examine the elements most critical to fostering student engagement and achievement. Utilizing the experience sampling method, time use diaries were obtained from 95 lower socioeconomic status African-American, Caucasian, and Mexican-American ninth-grade students over the period of one week to measure need fulfillment, the balance between challenge and skill, and emotional/psychological engagement across three activity settings—academic, active leisure, and passive leisure. An additional rating of behavioral engagement was obtained via teacher ratings. Significant differences were found in how students rated the fulfillment of the needs for autonomy, relatedness, and competence, as well as the balance between challenge and skill and emotional/psychological engagement across the activity settings. Students reported the greatest autonomy during all leisure activities and greater relatedness during active leisure than during passive leisure activities. Students reported greater levels of competence during active leisure than during academic activities and the highest levels of balance between challenge and skill were achieved during active leisure and academic activities. In terms of emotional/psychological engagement, students reported the highest levels during active leisure, followed by passive leisure, and finally academic activities. Taken together, student ratings of autonomy, relatedness, competence, and the balance between challenge and skill explained a significant amount of the variance in emotional/psychological engagement and, to a lesser degree, behavioral engagement. Further, when entered as separate sets of predictors, student ratings of autonomy, relatedness, and competence explained a significant amount of the variance in emotional/psychological engagement above and beyond that of the balance between challenge and skill. Although student ratings of autonomy, relatedness, competence, and the balance between challenge and skill were significant predictors of achievement when considered together, emotional/psychological engagement was not a strong predictor of achievement. However, behavioral engagement as rated by teachers did relate strongly with achievement. Implications and future directions are discussed.