The variable success in learning a second language (L2) may be best explained by varying degrees of motivation. This study investigated whether individual differences in appraisal dimensions of motivation explained explicit and implicit syntactic knowledge. Participants learned three syntactic structures under implicit and explicit training conditions. They also completed two motivation questionnaires before instruction. Syntactic development was assessed at early and late stages of acquisition. Results indicated superior performance on the tests of explicit knowledge, but a limited effect for the role of motivation in its development. However, with improvement in implicit knowledge at delayed testing, positive relationships emerged with several motivational dimensions. The results support L2 theoretical perspectives that posit different roles for explicit and implicit knowledge at early and late stages of L2 grammar, respectively. The findings also indicate that variation in learners' patterns of stimulus appraisals may contribute to variable success in the development of implicit knowledge.