The field of Heritage Language has experienced a great deal of advancement in the past few decades. Much research effort has been dedicated to analyzing and understanding different aspects of heritage language speakers, but less work has been done in the topic of pedagogical approaches. The few recent studies on pedagogical approaches have focused on the “how” of instruction of grammatical points in the heritage language classroom but dedicated less research efforts to an overall and comprehensive approach to classroom teaching and learning at the higher education level. Heritage language learners require teaching methodologies that differ from those used with second language students given their unique characteristics and needs. Having a curriculum and class materials that align to the needs of the students is essential in aiding the development and maintenance of the heritage language of the students. This study explores whether the implementation of a Project-Based Learning (PBL) curriculum can result in measurable gains in the development of written and oral skills in intermediate Spanish heritage language students, when compared to a control group that follows a traditional non-project-based methodology. Fluency, complexity, and accuracy in the written and oral samples were analyzed through a variety of indicators. The data collection consisted of a pre, and post writing and oral sample obtained at the beginning and end of the semester. The results showed that the students in the PBL curriculum achieved greater gains in their written skills when compared to the control group but had no effect on oral skills. The PBL group made significant gains in written fluency and complexity, and moderate gains in accuracy. The control group showed moderate gains in written fluency and complexity, and no improvement in accuracy. Neither group achieved statistically significant gains in oral fluency, complexity, or accuracy after one semester of instruction. The results offer implications for the impact that a PBL curriculum can have on heritage language learner’s linguistic development.