In this study we compared second language (L2) vocabulary learning with real objects versus nonobjects as referents (a) to test the effects of increased semantic processing (when learning nonobjects) and (b) to assess the viability of using L2 vocabulary learning with nonobjects (which forces learners toward concept mediation) for future studies on the development of conceptual mediation. Native English speakers attempted to learn 24 pseudowords using real objects and nonobjects as referents. After the learning phase, they completed two posttests: picture-to-L2 recall (productive) and word-picture verification (receptive). Scores were submitted to analyses of variance with condition (object, nonobject) as a within-subject independent variable. Other analyses tested whether object familiarity and nonobject similarity ratings had an effect on participants’ ability to learn the words. Regression analyses were used to test whether condition (object, nonobject) affected the participants’ accuracy in learning the words on the word-picture verification task. Additional analyses were also performed on the extent to which the mismatch between learning and testing as objects and nonobjects affected accuracy. The results of the study suggest that (a) the additional semantic processing involved in learning with nonobjects decreases learners’ ability to learn new word forms and that (b) L2 vocabulary learning with objects and nonobjects is a viable experimental paradigm for measuring the extent to which L2 vocabulary learning involves L1 lexical mediation.