Children with developmental language disorder (DLD) exhibit weaknesses in the syntactic aspects of language that affect their spoken language (i.e., speaking and listening) and written language (i.e., reading and writing). Speech-language pathologists (SLP) who work with children with DLD are the team member with the greatest expertise in syntax. However, emerging data suggest that speech-language pathology (SLP) students and SLPs have limitations in their explicit syntax knowledge that may affect how they assess and treat the language and literacy knowledge and skills of children with DLD. Additionally, there is a lack of data on the outcomes of professional development specific to syntax. This paper reports on the effects of self-paced, online learning modules on SLP graduate students' explicit syntax knowledge. Thirty-six SLP graduate students completed online syntax learning modules that taught four pairs of syntactic structures. SLP graduate students experienced a treatment effect from two of the four online training modules. Treatment effects seemed to be influenced by the syntactic skill being treated, by prior knowledge of that particular syntactic structure, and by other environmental factors, including training program. Although future studies should explore these factors further, the outcomes of this pilot study are the first to report on a way to improve SLP graduate students', and potentially SLPs', explicit syntax knowledge.